Bibliography.—References to the works of the above authors, and to many others, will be found underHexapodaand the special articles on various insect orders. Valuable summaries of the labours of Malpighi, Swammerdam and other early entomologists are given in L.C. Miall and A. Denny’sCockroach(London, 1886), and L. Henneguy’sLes Insectes(Paris, 1904).
Bibliography.—References to the works of the above authors, and to many others, will be found underHexapodaand the special articles on various insect orders. Valuable summaries of the labours of Malpighi, Swammerdam and other early entomologists are given in L.C. Miall and A. Denny’sCockroach(London, 1886), and L. Henneguy’sLes Insectes(Paris, 1904).
(G. H. C.)
ENTOMOSTRACA.This zoological term, as now restricted, includes the Branchiopoda, Ostracoda and Copepoda. The Ostracoda have the body enclosed in a bivalve shell-covering, and normally unsegmented. The Branchiopoda have a very variable number of body-segments, with or without a shield, simple or bivalved, and some of the postoral appendages normally branchial. The Copepoda have normally a segmented body, not enclosed in a bivalved shell-covering, the segments not exceeding eleven, the limbs not branchial.
Under the headingCrustaceathe Entomostraca have already been distinguished not only from the Thyrostraca or Cirripedes, but also from the Malacostraca, and an intermediate group of which the true position is still disputed. The choice is open to maintain the last as an independent subclass, and to follow Claus in calling it the Leptostraca, or to introduce it among the Malacostraca as the Nebaliacea, or with Packard and Sars to make it an entomostracan subdivision under the title Phyllocarida. At present it comprises the single familyNebaliidae. The bivalved carapace has a jointed rostrum, and covers only the front part of the body, to which it is only attached quite in front, the valve-like sides being under control of an adductor muscle. The eyes are stalked and movable. The first antennae have a lamellar appendage at the end of the peduncle, a decidedly non-entomostracan feature. The second antennae, mandibles and two pairs of maxillae may also be claimed as of malacostracan type. To these succeed eight pairs of foliaceous branchial appendages on the front division of the body, followed on the hind division by four pairs of powerful bifurcate swimming feet and two rudimentary pairs, the number, though not the nature, of these appendages being malacostracan. On the other hand, the two limbless segments that precede the caudal furca are decidedly non-malacostracan. The family was long limited to the single genusNebalia(Leach), and the single speciesN. bipes(O. Fabricius). Recently Sars has added a Norwegian species,N. typhlops, not blind but weak-eyed. There are also now two more genera,Paranebalia(Claus, 1880), in which the branchial feet are much longer than inNebalia, andNebaliopsis(Sars, 1887), in which they are much shorter. All the species are marine.
Branchiopoda.—In this order, exclusion of the Phyllocarida will leave three suborders of very unequal extent, the Phyllopoda, Cladocera, Branchiura. The constituents of the last have often been classed as Copepoda, and among the Branchiopods must be regarded as aberrant, since the “branchial tail” implied in the name has no feet, and the actual feet are by no means obviously branchial.
Phyllopoda.—This “leaf-footed” suborder has the appendages which follow the second maxillae variable in number, but all foliaceous and branchial. The development begins with a free nauplius stage. In the outward appearance of the adults there is great want of uniformity, one set having their limbs sheltered by no carapace, another having a broad shield over most of them, and a third having a bivalved shell-cover within which the whole body can be enclosed. In accord with these differences the sections may be named Gymnophylla, Notophylla, Conchophylla. The equivalent terms applied by Sars are Anostraca, Notostraca, Conchostraca, involving a termination already appropriated to higher divisions of the Crustacean class, for which it ought to be reserved.
1. Gymnophylla.—These singular crustaceans have long soft flexible bodies, the eyes stalked and movable, the first antennae small and filiform, the second lamellar in the female, in the male prehensile; this last character gives rise to some very fanciful developments. There are three families, two of which form companies rather severely limited. Thus thePolyartemiidae, which compensate themselves for their stumpy little tails by having nineteen instead of the normal eleven pairs of branchial feet, consist exclusively ofPolyartemia forcipata(Fischer, 1851). This species from the high north of Europe and Asia carries green eggs, and above them a bright pattern in ultramarine (Sars, 1896, 1897). TheThamnocephalidaehave likewise but a single species,Thamnocephalus platyurus(Packard, 1877), which justifies its title “bushy-head of the broad tail” by a singularity at each end. Forward from the head extends a long ramified appendage described as the “frontal shrub,” backward from the fourth abdominal segment of the male spreads a fin-like expansion which is unique. In the ravines of Kansas, pools supplied by torrential rains give birth to these and many other phyllopods, and in turn “millions of them perish by the drying up of the pools in July” (Packard). The remaining family, theBranchipodidae, includes eight genera. In the long familiarBranchipus,ChirocephalusandStreptocephalusthe males have frontal appendages, but these are wanting in the “brine-shrimp”Artemia, and the same want helps to distinguishBranchinecta(Verrill, 1869) from the old genusBranchipus. OfBranchiopsyllus(Sars, 1897) the male is not yet known, but in his genera of the same date, the SiberianArtemiopsisand the South AfricanBranchipodopsis(1898), there is no such appendage. Of the last genus the type speciesB. hodgsonibelongs to Cape Colony, but the specimens described were born and bred and observed in Norway. For the study of fresh-water Entomostraca large possibilities are now opened to the naturalist. A parcel of dried mud, coming for example from Palestine or Queensland, and after an indefinite interval of time put into water in England or elsewhere, may yield him living forms, both new and old, in the most agreeable variety. Some caution should be used against confounding accidentally introduced indigenous species with those reared from the imported eggs. Those, too, who send or bring the foreign soil should exercise a little thought in the choice of it, since dry earth that has never had any Entomostraca near it at home will not become fertile in them by the mere fact of exportation.2. Notophylla.—In this division the body is partly covered by a broad shield, united in front with the head; the eyes are sessile, the first antennae are small, the second rudimentary or wanting; of the numerous feet, sometimes sixty-three pairs, exceeding the number of segments to which they are attached, the first pair are more or less unlike the rest, and in the female the eleventh have the epipod and exopod (flabellum and sub-apical lobe of Lankester) modified to form an ovisac. Development begins with a nauplius stage. Males are very rare. The single familyApodidaecontains only two genera,Apusand its very near neighbourLepidurus.Apus australiensis(Spencer and Hall, 1896) may rank as the largest of the Entomostraca, reaching in the male, from front of shield to end of telson, a length of 70 mm., in the female of 64 mm. In a few days, or at most a fortnight, after a rainfall numberless specimens of these sizes were found swimming about, “and as not a single one was to be found in the water-pools prior to the rain, these must have been developed from the egg.” Similarly, in Northern IndiaApus himalayanuswas “collected from a stagnant pool in a jungle four days after a shower of rain had fallen,” following a drought of four months (Packard).3. Conchophylla.—Though concealed within the bivalved shell-cover, the mouth-parts are nearly as in the Gymnophylla, but the flexing of the caudal part is in contrast, and the biramous second antennae correspond with what is only a larval character in the other phyllopods. In the male the first one or two pairs of feet are modified into grasping organs. The small ova are crowded beneath the dorsal part of the valves. The development usually begins with a nauplius stage (Sars, 1896, 1900). There are four families: (a) TheLimnadiidae, with feet from 18 to 32 pairs, comprise four (or five) genera. Of theseLimnadella(Girard, 1855) has a single eye. It remains rather obscure, though the type species originally “was discovered in great abundance in a roadside puddle subject to desiccation.”Limnadia(Brongniart, 1820) is supposed to consist of species exclusively parthenogenetic. But when asked to believe that males never occur among these amazons, one cannot but remember how hard it is to prove a negative. (b) TheLynceidae, with not more than twelve pairs of feet. This family is limited to the species, widely distributed, of the single genusLynceus, established by O.F. Müller in 1776 and 1781, and first restricted by Leach in 1816 in theEncyclopaedia Britannica(art. “Annulosa,” of that edition). Leach there assigns to it the single speciesL. brachyurus(Müller), and as this is included in the genusLimnetis(Lovén, 1846), that genus must be a synonym ofLynceusas restricted. (c)Leptestheriidae.Estheria(Rüppell, 1837) was instituted for the speciesdahalacensis, which Sars includes in his genusLeptestheria(1898); butEstheriawas already appropriated, and of its synonymsCyzicus(Audouin, 1837) is lost for vagueness, whileIsaura(Joly, 1842) is also appropriated, so thatLeptestheriabecomes the name of the typical genus, and determines the name of the family. (d)Cyclestheriidae. This family consists of the single speciesCyclestheria hislopi(Baird), reported from India, Ceylon, Celebes, Australia, East Africa and Brazil. Sars (1887) having had the opportunity of raising it from dried Australian mud, found that, unlike other phyllopods, but like the Cladocera, the parent keeps its brood within the shell until their full development.
1. Gymnophylla.—These singular crustaceans have long soft flexible bodies, the eyes stalked and movable, the first antennae small and filiform, the second lamellar in the female, in the male prehensile; this last character gives rise to some very fanciful developments. There are three families, two of which form companies rather severely limited. Thus thePolyartemiidae, which compensate themselves for their stumpy little tails by having nineteen instead of the normal eleven pairs of branchial feet, consist exclusively ofPolyartemia forcipata(Fischer, 1851). This species from the high north of Europe and Asia carries green eggs, and above them a bright pattern in ultramarine (Sars, 1896, 1897). TheThamnocephalidaehave likewise but a single species,Thamnocephalus platyurus(Packard, 1877), which justifies its title “bushy-head of the broad tail” by a singularity at each end. Forward from the head extends a long ramified appendage described as the “frontal shrub,” backward from the fourth abdominal segment of the male spreads a fin-like expansion which is unique. In the ravines of Kansas, pools supplied by torrential rains give birth to these and many other phyllopods, and in turn “millions of them perish by the drying up of the pools in July” (Packard). The remaining family, theBranchipodidae, includes eight genera. In the long familiarBranchipus,ChirocephalusandStreptocephalusthe males have frontal appendages, but these are wanting in the “brine-shrimp”Artemia, and the same want helps to distinguishBranchinecta(Verrill, 1869) from the old genusBranchipus. OfBranchiopsyllus(Sars, 1897) the male is not yet known, but in his genera of the same date, the SiberianArtemiopsisand the South AfricanBranchipodopsis(1898), there is no such appendage. Of the last genus the type speciesB. hodgsonibelongs to Cape Colony, but the specimens described were born and bred and observed in Norway. For the study of fresh-water Entomostraca large possibilities are now opened to the naturalist. A parcel of dried mud, coming for example from Palestine or Queensland, and after an indefinite interval of time put into water in England or elsewhere, may yield him living forms, both new and old, in the most agreeable variety. Some caution should be used against confounding accidentally introduced indigenous species with those reared from the imported eggs. Those, too, who send or bring the foreign soil should exercise a little thought in the choice of it, since dry earth that has never had any Entomostraca near it at home will not become fertile in them by the mere fact of exportation.
2. Notophylla.—In this division the body is partly covered by a broad shield, united in front with the head; the eyes are sessile, the first antennae are small, the second rudimentary or wanting; of the numerous feet, sometimes sixty-three pairs, exceeding the number of segments to which they are attached, the first pair are more or less unlike the rest, and in the female the eleventh have the epipod and exopod (flabellum and sub-apical lobe of Lankester) modified to form an ovisac. Development begins with a nauplius stage. Males are very rare. The single familyApodidaecontains only two genera,Apusand its very near neighbourLepidurus.Apus australiensis(Spencer and Hall, 1896) may rank as the largest of the Entomostraca, reaching in the male, from front of shield to end of telson, a length of 70 mm., in the female of 64 mm. In a few days, or at most a fortnight, after a rainfall numberless specimens of these sizes were found swimming about, “and as not a single one was to be found in the water-pools prior to the rain, these must have been developed from the egg.” Similarly, in Northern IndiaApus himalayanuswas “collected from a stagnant pool in a jungle four days after a shower of rain had fallen,” following a drought of four months (Packard).
3. Conchophylla.—Though concealed within the bivalved shell-cover, the mouth-parts are nearly as in the Gymnophylla, but the flexing of the caudal part is in contrast, and the biramous second antennae correspond with what is only a larval character in the other phyllopods. In the male the first one or two pairs of feet are modified into grasping organs. The small ova are crowded beneath the dorsal part of the valves. The development usually begins with a nauplius stage (Sars, 1896, 1900). There are four families: (a) TheLimnadiidae, with feet from 18 to 32 pairs, comprise four (or five) genera. Of theseLimnadella(Girard, 1855) has a single eye. It remains rather obscure, though the type species originally “was discovered in great abundance in a roadside puddle subject to desiccation.”Limnadia(Brongniart, 1820) is supposed to consist of species exclusively parthenogenetic. But when asked to believe that males never occur among these amazons, one cannot but remember how hard it is to prove a negative. (b) TheLynceidae, with not more than twelve pairs of feet. This family is limited to the species, widely distributed, of the single genusLynceus, established by O.F. Müller in 1776 and 1781, and first restricted by Leach in 1816 in theEncyclopaedia Britannica(art. “Annulosa,” of that edition). Leach there assigns to it the single speciesL. brachyurus(Müller), and as this is included in the genusLimnetis(Lovén, 1846), that genus must be a synonym ofLynceusas restricted. (c)Leptestheriidae.Estheria(Rüppell, 1837) was instituted for the speciesdahalacensis, which Sars includes in his genusLeptestheria(1898); butEstheriawas already appropriated, and of its synonymsCyzicus(Audouin, 1837) is lost for vagueness, whileIsaura(Joly, 1842) is also appropriated, so thatLeptestheriabecomes the name of the typical genus, and determines the name of the family. (d)Cyclestheriidae. This family consists of the single speciesCyclestheria hislopi(Baird), reported from India, Ceylon, Celebes, Australia, East Africa and Brazil. Sars (1887) having had the opportunity of raising it from dried Australian mud, found that, unlike other phyllopods, but like the Cladocera, the parent keeps its brood within the shell until their full development.
Cladocera.—In this suborder the head is more or less distinct, the rest of the body being in general laterally compressed and covered by a bivalved test. The title “branching horns” alludes to the second antennae, which are two-branched except in the females ofHolopedium, with each branch setiferous, composed of only two to four joints. The mandibles are without palp. The pairs of feet are four to six. The eye is single, and in addition to the eye there is often an “eye-spot,”Monospilusbeing unique in having the eye-spot alone and no eye, whileLeydigiopsis(Sars, 1901) has an eye with an eye-spot equal to it or larger. The heart has a pair of venous ostia, often blending into one, and an anterior arterial aorta. Respiration is conducted by the general surface, by the branchial lamina (external branch) of the feet, and the vesicular appendage (when present) at the base of this branch. The “abdomen,” behind the limbs, is usually very short, occasionally very long. The “postabdomen,” marked off by the two postabdominal setae, usually has teeth or spines, and ends in two denticulate or ciliate claws, or it may be rudimentary, as inPolyphemus. Many species have a special glandular organ at the back of the head, whichSida crystallinauses for attaching itself to various objects. The Leydigian or nuchal organ is supposed to be auditory and to contain an otolith. The female lays two kinds of eggs—“summer-eggs,” which develop without fertilization, and “winter-eggs” or resting eggs, which require to be fertilized. The latter in theDaphniidaeare enclosed in a modified part of the mother’s shell, called the ephippium from its resemblance to a saddle in shape and position. In other families a less elaborate case has been observed, for which Scourfield has proposed the term protoephippium. InLeydigiahe has recently found a structure almost as complex as that of theDaphniidae. In some families the resting eggs escape into the water without special covering. Only the embryos ofLeptodoraare known to hatch out in the nauplius stage.Penilia(Dana, 1849) is perhaps the only exclusively marine genus. The great majority of the Cladocera belong to fresh water, but their adaptability is large, sinceMoina rectirostris(O.F. Müller) can equally enjoy a pond at Blackheath, and near Odessa live in water twice as salt as that of the ocean. In point of size a Cladoceran of 5 mm. is spoken of as colossal.
Dr Jules Richard in his revision (1895) retains the sections proposed by Sars in 1865, Calyptomera and Gymnomera. The former, with the feet for the most part concealed by the carapace, is subdivided into two tribes, the Ctenopoda, or “comb-feet,” in which the six pairs of similar feet, all branchial and nonprehensile, are furnished with setae arranged like the teeth of a comb, and the Anomopoda, or “variety-feet,” in which the front feet differ from the rest by being more or less prehensile, without branchial laminae.The Ctenopoda comprise two families: (a) theHolopediidae, with a solitary species,Holopedium gibberum(Zaddach), queerly clothed in a large gelatinous involucre, and found in mountain tarns all over Europe, in large lakes of N. America, and also in shallow ponds and waters at sea-level; (b) theSididae, with no such involucre, but with seven genera, and rather more than twice as many species. OfDiaphanosoma modiglianiiRichard says that at different points of Lake Toba in Sumatra millions of specimens were obtained, among which he had not met with a single male.The Anomopoda are arranged in four families, all but one very extensive. (a)Daphniidae. Of the seven genera, the cosmopolitanDaphniacontains about 100 species and varieties, of which Thomas Scott (1899) observes that “scarcely any of the several characters that have at one time or another been selected as affording a means for discriminating between the different forms can be relied on as satisfactory.” Though this may dishearten the systematist, Scourfield (1900) reminds us that “It was in a water-flea that Metschnikoff first saw the leucocytes (or phagocytes) trying to get rid of disease germs by swallowing them, and was so led to his epoch-making discovery of the part played by these minute amoeboid corpuscles in the animal body.” ForScapholeberis mucronata(O.F. Müller), Scourfield has shown how it is adapted for movement back downwards in the water along the underside of the surface film, which to many small crustaceans is a dangerously disabling trap. (b)Bosminidae. ToBosmina(Baird, 1845) Richard addedBosminopsisin 1895. (c)Macrotrichidae.In this familyMacrothrix(Baird, 1843) is the earliest genus, among the latest beingGrimaldina(Richard, 1892) andJheringula(Sars, 1900). Dried mud and vegetable débris from S. Paulo in Brazil supplied Sars with representatives of all the three in his Norwegian aquaria, in some of which the littleMacrothrix elegans“multiplied to such an extraordinary extent as at last to fill up the water with immense shoals of individuals.” “The appearance of male specimens was always contemporary with the first ephippial formation in the females.” ForStreblocerus pygmaeus, grown under the same conditions, Sars observes: “This is perhaps the smallest of the Cladocera known, and is hardly more than visible to the naked eye,” the adult female scarcely exceeding 0.25 mm. Yet in the next familyAlonella nana(Baird) disputes the palm and claims to be the smallest of all known Arthropoda. (d)Chydoridae.This family, so commonly calledLynceidae, contains a large number of genera, among which one may usually search in vain, and rightly so, for the genusLynceus. The key to the riddle is to be found in theEncyclopaedia Britannicafor 1816. There, as above explained, Leach began the subdivision of Müller’s too comprehensive genus, the result being thatLynceusbelongs to the Phyllopoda, andChydorus(Leach, 1816) properly gives its name to the present family, in which the doubly convoluted intestine is so remarkable. Of its many genera,Leydigia,Leydigiopsis,Monospilushave been already mentioned.Dadaya macrops(Sars, 1901), from South America and Ceylon, has a very large eye and an eye-spot fully as large, but it is a very small creature, odd in its behaviour, moving by jumps at the very surface of the water. “To the naked eye it looked like a little black atom darting about in a most wonderful manner.”Fig. 1.—Dolops ranarum(Stuhlmann).The Gymnomera, with a carapace too small to cover the feet, which are all prehensile, are divided also into two tribes, the Onychopoda, in which the four pairs of feet have a toothed maxillary process at the base, and the Haplopoda, in which there are six pairs of feet, without such a process. To thePolyphemidae, the well-known family of the former tribe, Sars in 1897 added two remarkable genera,Cercopagis, meaning “tail with a sling,” andApagis, “without a sling,” for seven species from the Sea of Azov. The Haplopoda likewise have but a single family, theLeptodoridae, and this has but the single genusLeptodora(Lilljeborg, 1861). Dr Richard (1895, 1896) gives a Cladoceran bibliography of 601 references.
Dr Jules Richard in his revision (1895) retains the sections proposed by Sars in 1865, Calyptomera and Gymnomera. The former, with the feet for the most part concealed by the carapace, is subdivided into two tribes, the Ctenopoda, or “comb-feet,” in which the six pairs of similar feet, all branchial and nonprehensile, are furnished with setae arranged like the teeth of a comb, and the Anomopoda, or “variety-feet,” in which the front feet differ from the rest by being more or less prehensile, without branchial laminae.
The Ctenopoda comprise two families: (a) theHolopediidae, with a solitary species,Holopedium gibberum(Zaddach), queerly clothed in a large gelatinous involucre, and found in mountain tarns all over Europe, in large lakes of N. America, and also in shallow ponds and waters at sea-level; (b) theSididae, with no such involucre, but with seven genera, and rather more than twice as many species. OfDiaphanosoma modiglianiiRichard says that at different points of Lake Toba in Sumatra millions of specimens were obtained, among which he had not met with a single male.
The Anomopoda are arranged in four families, all but one very extensive. (a)Daphniidae. Of the seven genera, the cosmopolitanDaphniacontains about 100 species and varieties, of which Thomas Scott (1899) observes that “scarcely any of the several characters that have at one time or another been selected as affording a means for discriminating between the different forms can be relied on as satisfactory.” Though this may dishearten the systematist, Scourfield (1900) reminds us that “It was in a water-flea that Metschnikoff first saw the leucocytes (or phagocytes) trying to get rid of disease germs by swallowing them, and was so led to his epoch-making discovery of the part played by these minute amoeboid corpuscles in the animal body.” ForScapholeberis mucronata(O.F. Müller), Scourfield has shown how it is adapted for movement back downwards in the water along the underside of the surface film, which to many small crustaceans is a dangerously disabling trap. (b)Bosminidae. ToBosmina(Baird, 1845) Richard addedBosminopsisin 1895. (c)Macrotrichidae.In this familyMacrothrix(Baird, 1843) is the earliest genus, among the latest beingGrimaldina(Richard, 1892) andJheringula(Sars, 1900). Dried mud and vegetable débris from S. Paulo in Brazil supplied Sars with representatives of all the three in his Norwegian aquaria, in some of which the littleMacrothrix elegans“multiplied to such an extraordinary extent as at last to fill up the water with immense shoals of individuals.” “The appearance of male specimens was always contemporary with the first ephippial formation in the females.” ForStreblocerus pygmaeus, grown under the same conditions, Sars observes: “This is perhaps the smallest of the Cladocera known, and is hardly more than visible to the naked eye,” the adult female scarcely exceeding 0.25 mm. Yet in the next familyAlonella nana(Baird) disputes the palm and claims to be the smallest of all known Arthropoda. (d)Chydoridae.This family, so commonly calledLynceidae, contains a large number of genera, among which one may usually search in vain, and rightly so, for the genusLynceus. The key to the riddle is to be found in theEncyclopaedia Britannicafor 1816. There, as above explained, Leach began the subdivision of Müller’s too comprehensive genus, the result being thatLynceusbelongs to the Phyllopoda, andChydorus(Leach, 1816) properly gives its name to the present family, in which the doubly convoluted intestine is so remarkable. Of its many genera,Leydigia,Leydigiopsis,Monospilushave been already mentioned.Dadaya macrops(Sars, 1901), from South America and Ceylon, has a very large eye and an eye-spot fully as large, but it is a very small creature, odd in its behaviour, moving by jumps at the very surface of the water. “To the naked eye it looked like a little black atom darting about in a most wonderful manner.”
The Gymnomera, with a carapace too small to cover the feet, which are all prehensile, are divided also into two tribes, the Onychopoda, in which the four pairs of feet have a toothed maxillary process at the base, and the Haplopoda, in which there are six pairs of feet, without such a process. To thePolyphemidae, the well-known family of the former tribe, Sars in 1897 added two remarkable genera,Cercopagis, meaning “tail with a sling,” andApagis, “without a sling,” for seven species from the Sea of Azov. The Haplopoda likewise have but a single family, theLeptodoridae, and this has but the single genusLeptodora(Lilljeborg, 1861). Dr Richard (1895, 1896) gives a Cladoceran bibliography of 601 references.
Branchiura.—This term was introduced by Thorell in 1864 for theArgulidae, a family which had been transferred to the Branchiopoda by Zenker in 1854, though sometimes before and since united with the parasitic Copepoda. Though the animals have an oral siphon, they do not carry ovisacs like the siphonostomous copepods, but glue their eggs in rows to extraneous objects. Their lateral, compound, feebly movable eyes agree with those of the Phyllopoda. The family are described by Claus as“intermittent parasites,” because when gorged they leave their hosts, fishes or frogs, and swim about in freedom for a considerable period. The long-knownArgulus(O.F. Müller) has the second maxillae transformed into suckers, but inDolops(Audouin, 1837) (fig. 1), the name of which supersedes the more familiarGyropeltis(Heller, 1857), these effect attachment by ending in strong hooks (Bouvier, 1897). A third genus,Chonopeltis(Thiele, 1900), has suckers, but has lost its first antennae, at least in the female.
Ostracoda.—The body, seldom in any way segmented, is wholly encased in a bivalved shell, the caudal part strongly inflexed, and almost always ending in a furca. The limbs, including antennae and mouth organs, never exceed seven definite pairs. The first antennae never have more than eight joints. The young usually pass through several stages of development after leaving the egg, and this commonly after, even long after, the egg has left the maternal shell. Parthenogenesis is frequent.
The four tribes instituted by Sars in 1865 were reduced to two by G.W. Müller in 1894, the Myodocopa, which almost always have a heart, and the Podocopa, which have none.
Myodocopa.—These have the furcal branches broad, lamellar, with at least three pairs of strong spines or ungues. Almost always the shell has a rostral sinus. Müller divides the tribe into three families,Cypridinidae, Halocypridae, and the heartlessPolycopidae, which constituted the tribe Cladocopa of Sars. From the first of these Brady and Norman distinguish the Asteropidae (fig. 3), remarkable for seven pairs of long branchial leaves which fold over the hinder extremity of the animal, and theSarsiellidae, still somewhat obscure, besides adding theRutidermatidae, knowledge of which is based on skilful maceration of minute and long-dried specimens. TheHalocypridaeare destitute of compound lateral eyes, and have the sexual orifice unsymmetrically placed.Podocopa.—In these the furcal branches are linear or rudimentary, the shell is without rostral sinus, and, besides distinguishing characters of the second antennae, they have always a branchial plate well developed on the first maxillae, which is inconstant in the other tribe. There are five families: (a)Cyprididae(? includingCypridopsidaeof Brady and Norman). In some of the genera parthenogenetic propagation is carried to such an extent that of the familiarCyprisit is said, “until quite lately males in this genus were unknown; and up to the present time no male has been found in the British Islands” (Brady and Norman, 1896). On the other hand, the ejaculatory duct with its verticillate sac in the male ofCyprisand other genera is a feature scarcely less remarkable. (b)Bairdiidae, which have the valves smooth, with the hinge untoothed. (c)Cytheridae(? includingParadoxostomatidaeof Brady and Norman), in which the valves are usually sculptured, with toothed hinge. Of this family the members are almost exclusively marine, butLimnicythereis found in fresh water, andXestoleberis bromeliarum(Fritz Müller) lives in the water that collects among the leaves of Bromelias, plants allied to the pine-apples. (d)Darwinulidae, including the single speciesDarwinula stevensoni, Brady and Robertson, described as “perhaps the most characteristic Entomostracan of the East Anglian Fen District.” (e)Cytherellidae, which, unlike the Ostracoda in general, have the hinder part of the body segmented, at least ten segments being distinguishable in the female. They have the valves broad at both ends, and were placed by Sars in a separate tribe, called Platycopa.
Myodocopa.—These have the furcal branches broad, lamellar, with at least three pairs of strong spines or ungues. Almost always the shell has a rostral sinus. Müller divides the tribe into three families,Cypridinidae, Halocypridae, and the heartlessPolycopidae, which constituted the tribe Cladocopa of Sars. From the first of these Brady and Norman distinguish the Asteropidae (fig. 3), remarkable for seven pairs of long branchial leaves which fold over the hinder extremity of the animal, and theSarsiellidae, still somewhat obscure, besides adding theRutidermatidae, knowledge of which is based on skilful maceration of minute and long-dried specimens. TheHalocypridaeare destitute of compound lateral eyes, and have the sexual orifice unsymmetrically placed.
Podocopa.—In these the furcal branches are linear or rudimentary, the shell is without rostral sinus, and, besides distinguishing characters of the second antennae, they have always a branchial plate well developed on the first maxillae, which is inconstant in the other tribe. There are five families: (a)Cyprididae(? includingCypridopsidaeof Brady and Norman). In some of the genera parthenogenetic propagation is carried to such an extent that of the familiarCyprisit is said, “until quite lately males in this genus were unknown; and up to the present time no male has been found in the British Islands” (Brady and Norman, 1896). On the other hand, the ejaculatory duct with its verticillate sac in the male ofCyprisand other genera is a feature scarcely less remarkable. (b)Bairdiidae, which have the valves smooth, with the hinge untoothed. (c)Cytheridae(? includingParadoxostomatidaeof Brady and Norman), in which the valves are usually sculptured, with toothed hinge. Of this family the members are almost exclusively marine, butLimnicythereis found in fresh water, andXestoleberis bromeliarum(Fritz Müller) lives in the water that collects among the leaves of Bromelias, plants allied to the pine-apples. (d)Darwinulidae, including the single speciesDarwinula stevensoni, Brady and Robertson, described as “perhaps the most characteristic Entomostracan of the East Anglian Fen District.” (e)Cytherellidae, which, unlike the Ostracoda in general, have the hinder part of the body segmented, at least ten segments being distinguishable in the female. They have the valves broad at both ends, and were placed by Sars in a separate tribe, called Platycopa.
The range in time of the Ostracoda is so extended that, in G.W. Müller’s opinion, their separation into the families now living may have already taken place in the Cambrian period. Their range in space, including carriage by birds, may be coextensive with the distribution of water, but it is not known what height of temperature or how much chemical adulteration of the water they can sustain, how far they can penetrate underground, nor what are the limits of their activity between the floor and the surface of aquatic expanses, fresh or saline. In individual size they have never been important, and of living forms the largest is one of recent discovery,Crossophorus africanus, a Cypridinid about three-fifths of an inch (15.5 mm.) long; but a length of one or two millimetres is more common, and it may descend to the seventy-fifth of an inch. By multitude they have been, and still are, extremely important.
M, End of adductor muscle.
OC, Eye.
AI, Second antenna.
MX. 1, First maxilla.
MX. 2, Second maxilla.
P. 1, First foot.
V.O, Vermiform organ.
BR, Seven branchial leaves.
F, Projecting ungues of the furca.
Though the exterior is more uniform than in most groups of Crustacea, the bivalved shell or carapace may be strongly calcified and diversely sculptured (fig. 2), or membranaceous and polished, hairy or smooth, oval or round or bean-shaped, or of some less simple pattern; the valves may fit neatly, or one overlap the other, their hinge may have teeth or be edentulous, and their front part may be excavated for the protrusion of the antennae or have no such “rostral sinus.” By various modifications of their valves and appendages the creatures have become adapted for swimming, creeping, burrowing, or climbing, some of them combining two or more of these activities, for which their structure seems at the first glance little adapted. Considering the imprisonment of the ostracod body within the valves, it is more surprising that theAsteropidaeandCypridinidaeshould have a pair of compound and sometimes large eyes, in addition to the median organ at the base of the “frontal tentacle,” than that other members of the group should be limited to that median organ of sight, or have no eyes at all. The median eye when present may have or not have a lens, and its three pigment-cups may be close together or wide apart and the middle one rudimentary. As might be expected, in thickened and highly embossed valves thin spaces occur over the visual organ. The frontal organ varies in form and apparently in function, and is sometimes absent. The first antennae, according to the family, may assist in walking, swimming, burrowing, climbing, grasping, and besides they carry sensory setae, and sometimes they have suckers on their setae (see Brady and Norman onCypridina norvegica). The second antennae are usually the chief motor-organs for swimming, walking and climbing. The mandibles are normally five-jointed, with remnants of an outer branch on the second joint, the biting edge varying from strong development to evanescence, the terminal joints or “palp” giving the organ a leg-like appearance and function, which disappears in suctorial genera such asParacytherois. The variable first maxillae are seldom pediform, their function being concerned chiefly with nutrition, sensation and respiration. The variability in form and function of the second maxillae is sufficiently shown by the fact that G.W. Müller, our leading authority, adopts the confusing plan of calling them second maxillae in theCypridinidae(includingAsteropidae), maxillipeds in theHalocypridaeandCyprididae, and first legs in theBairdiidae,Cytheridae,PolycopidaeandCytherellidae, so that in his fine monograph he uses the term first leg in two quite different senses. The first legs, meaning thereby the sixth pair of appendages, are generally pediform and locomotive, but sometimes unjointed, acting as a kind of brushes to cleanse the furca, while in thePolycopidaethey are entirely wanting. The second legs are sometimes wanting, sometimes pediform and locomotive, sometimes strangely metamorphosed into the “vermiform organ,” generally long, many-jointed, and distally armed with retroverted spines, its function being that of an extremely mobile cleansing foot, which can insert itself among the eggs in the brood-space, between the branchial leaves ofAsterope(fig. 3), and even range over the external surface of the valves. The “brush-formed” organs of the Podocopa are medially placed, and, in spite of their sometimes forward situation, Müller believes among other possibilities that they and the penis in theCypridinidaemay be alike remnants of a third pair of legs, not homologous with the penis of other Ostracoda (Podocopa included). The furca is, as a rule, a powerful motor-organ, and has its laminae edged with strong teeth (ungues) or setae or both. The young, though born with valves, have at first a nauplian body, and pass through various stages to maturity.Brady and Norman, in theirMonograph of the Ostracoda of the North Atlantic and North-Western Europe(1889), give a bibliography of 125 titles, and in the second part (1896) they give 55 more. The lists are not meant to be exhaustive, any more than G.W. Müller’s literature list of 125 titles in 1894. They do not refer to Latreille, 1802, with whom the term Ostracoda originates.
Though the exterior is more uniform than in most groups of Crustacea, the bivalved shell or carapace may be strongly calcified and diversely sculptured (fig. 2), or membranaceous and polished, hairy or smooth, oval or round or bean-shaped, or of some less simple pattern; the valves may fit neatly, or one overlap the other, their hinge may have teeth or be edentulous, and their front part may be excavated for the protrusion of the antennae or have no such “rostral sinus.” By various modifications of their valves and appendages the creatures have become adapted for swimming, creeping, burrowing, or climbing, some of them combining two or more of these activities, for which their structure seems at the first glance little adapted. Considering the imprisonment of the ostracod body within the valves, it is more surprising that theAsteropidaeandCypridinidaeshould have a pair of compound and sometimes large eyes, in addition to the median organ at the base of the “frontal tentacle,” than that other members of the group should be limited to that median organ of sight, or have no eyes at all. The median eye when present may have or not have a lens, and its three pigment-cups may be close together or wide apart and the middle one rudimentary. As might be expected, in thickened and highly embossed valves thin spaces occur over the visual organ. The frontal organ varies in form and apparently in function, and is sometimes absent. The first antennae, according to the family, may assist in walking, swimming, burrowing, climbing, grasping, and besides they carry sensory setae, and sometimes they have suckers on their setae (see Brady and Norman onCypridina norvegica). The second antennae are usually the chief motor-organs for swimming, walking and climbing. The mandibles are normally five-jointed, with remnants of an outer branch on the second joint, the biting edge varying from strong development to evanescence, the terminal joints or “palp” giving the organ a leg-like appearance and function, which disappears in suctorial genera such asParacytherois. The variable first maxillae are seldom pediform, their function being concerned chiefly with nutrition, sensation and respiration. The variability in form and function of the second maxillae is sufficiently shown by the fact that G.W. Müller, our leading authority, adopts the confusing plan of calling them second maxillae in theCypridinidae(includingAsteropidae), maxillipeds in theHalocypridaeandCyprididae, and first legs in theBairdiidae,Cytheridae,PolycopidaeandCytherellidae, so that in his fine monograph he uses the term first leg in two quite different senses. The first legs, meaning thereby the sixth pair of appendages, are generally pediform and locomotive, but sometimes unjointed, acting as a kind of brushes to cleanse the furca, while in thePolycopidaethey are entirely wanting. The second legs are sometimes wanting, sometimes pediform and locomotive, sometimes strangely metamorphosed into the “vermiform organ,” generally long, many-jointed, and distally armed with retroverted spines, its function being that of an extremely mobile cleansing foot, which can insert itself among the eggs in the brood-space, between the branchial leaves ofAsterope(fig. 3), and even range over the external surface of the valves. The “brush-formed” organs of the Podocopa are medially placed, and, in spite of their sometimes forward situation, Müller believes among other possibilities that they and the penis in theCypridinidaemay be alike remnants of a third pair of legs, not homologous with the penis of other Ostracoda (Podocopa included). The furca is, as a rule, a powerful motor-organ, and has its laminae edged with strong teeth (ungues) or setae or both. The young, though born with valves, have at first a nauplian body, and pass through various stages to maturity.
Brady and Norman, in theirMonograph of the Ostracoda of the North Atlantic and North-Western Europe(1889), give a bibliography of 125 titles, and in the second part (1896) they give 55 more. The lists are not meant to be exhaustive, any more than G.W. Müller’s literature list of 125 titles in 1894. They do not refer to Latreille, 1802, with whom the term Ostracoda originates.
Copepoda.—The body is not encased in a bivalved shell; its articulated segments are at most eleven, those behind the genital segment being without trace of limbs, but the last almost always carrying a furca. Sexes separate, fertilization by spermatophores. Ova in single or double or rarely severalpackets, attached as ovisacs or egg-strings to the genital openings, or enclosed in a dorsal marsupium, or deposited singly or occasionally in bundles. The youngest larvae are typical nauplii. The next, the copepodid or cyclopid, stage is characterized by a cylindrical segmented body, with fore- and hind-body distinct, and by having at most six cephalic limbs and two pairs of swimming feet.
The order thus defined (see Giesbrecht and Schmeil,Das Tierreich, 1898), with far over a thousand species (Hansen, 1900), embraces forms of extreme diversity, although, when species are known in all their phases and both sexes, they constantly tend to prove that there are no sharply dividing lines between the free-living, the semi-parasitic, and those which in adult life are wholly parasitic and then sometimes grotesquely unlike the normal standard. Giesbrecht and Hansen have shown that the mouth-organs consist of mandibles, first and second maxillae and maxillipeds; and Claus himself relinquished his long-maintained hypothesis that the last two pairs were the separated exopods and endopods of a single pair of appendages. Thorell’s classification (1859) of Gnathostoma, Poecilostoma, Siphonostoma, based on the mouth-organs, was long followed, though almost at the outset shown by Claus to depend on the erroneous supposition that the Poecilostoma were devoid of mandibles. Brady added a new section, Choniostomata, in 1894, and another, Leptostomata, in 1900, each for a single species. Canu in 1892 proposed two groups, Monoporodelphya and Diporodelphya, the copulatory openings of the female being paired in the latter, unpaired in the former. It may be questioned whether this distinction, however important in itself, would lead to a satisfactory grouping of families. In the same year Giesbrecht proposed his division of the order into Gymnoplea and Podoplea.
In appearance an ordinary Copepod is divided into fore- and hind-body, of its eleven segments the composite first being the head, the next five constituting the thorax, and the last five the abdomen. The coalescence of segments, though frequent, does not after a little experience materially confuse the counting. But there is this peculiarity, that the middle segment is sometimes continuous with the broader fore-body, sometimes with the narrower hind-body. In the former case the hind-body, consisting only of the abdomen, forms a pleon or tail-part devoid of feet, and the species so constructed are Gymnoplea, those of the naked or footless pleon. In the latter case the middle segment almost always carries with it to the hind-body a pair of rudimentary limbs, whence the term Podoplea, meaning species that have a pleon with feet. It may be objected that hereby the term pleon is used in two different senses, first applying to the abdomen alone and then to the abdomen plus the last thoracic segment. Even this verbal flaw would be obviated if Giesbrecht could prove his tentative hypothesis, that the Gymnoplea may have lost a pre-genital segment of the abdomen, and the Podoplea may have lost the last segment of the thorax. The classification is worked out as follows:—
1.Gymnoplea.—First segment of hind-body footless, bearing the orifices of the genital organs (in the male unsymmetrically placed); last foot of the fore-body in the male a copulatory organ; neither, or only one, of the first pair of antennae in the male geniculating; cephalic limbs abundantly articulated and provided with many plumose setae; heart generally present. Animals usually free-living, pelagic (Giesbrecht and Schmeil).This group, with 65 genera and four or five hundred species, is divided by Giesbrecht into tribes: (a) Amphaskandria. In this tribe the males have both antennae of the first pair as sensory organs. There is but one family, theCalanidae, but this is a very large one, with 26 genera and more than 100 species. Among them is the cosmopolitanCalanus finmarchicus, the earliest described (by Bishop Gunner in 1770) of all the marine free-swimming Copepoda. Among them also is the peacock Calanid,Calocalanus pavo(Dana), with its highly ornamented antennae and gorgeous tail, the most beautiful species of the whole order (fig. 4). (b) Heterarthrandria. Here the males have one or the other of the first pair of antennae modified into a grasping organ for holding the female. There are four families, theDiaptomidaewith 27 genera, thePontellidaewith 10, thePseudocyclopidaeandCandaciidaeeach with one genus. The first of these families is often calledCentropagidae, but, as Sars has pointed out,Diaptomus(Westwood, 1836) is the oldest genus in it. Of 177 species valid in the family Giesbrecht and Schmeil assign 67 toDiaptomus. In regard to one of its species Dr Brady says: “In one instance, at least (Talkin Tarn, Cumberland) I have seen the net come up from a depth of 6 or 8 ft. below the surface with a dense mass consisting almost entirely ofD. gracilis.” The length of this net-filling species is about a twentieth of an inch.Fig.4.—Calocalanus pavo(Dana).2.Podoplea.—The first segment of the hind-body almost always with rudimentary pair of feet; orifices of the genital organs (symmetrically placed in both sexes) in the following segment; neither the last foot of the fore-body nor the rudimentary feet just mentioned acting as a copulatory organ in the male; both or neither of the first pair of antennae in the male geniculating; cephalic limbs less abundantly articulated and with fewer plumose setae or none, but with hooks and clasping setae. Heart almost always wanting. Free-living (rarely pelagic) or parasitic (Giesbrecht and Schmeil).This group is also divided by Giesbrecht into two tribes, Ampharthrandria and Isokerandria. In 1892 he distinguished the former as those in which the first antennae of the male have both members modified for holding the female, and the genital openings of the female have a ventral position, sometimes in close proximity, sometimes strongly lateral; the latter as those in which the first antennae of the male are similar to those of the female, the function of holding her being transferred to the male maxillipeds, while the genital openings of the female are dorsal, though at times strongly lateral. In 1899, with a view to the many modifications exhibited by parasitic and semi-parasitic species, the definitions, stripped of a too hampering precision, took a different form: (a) Ampharthrandria. “Swimming Podoplea with geniculating first antennae in the male sex, and descendants of such; first antennae in female and male almost always differently articulated.” The families occupy fresh water as well as the sea. Naturally “descendants” which have lost the characteristic feature of the definition cannot be recognized without some further assistance than the definition supplies. Of the families comprised, theMormonillidaeconsist only ofMormonilla(Giesbrecht), and are not mentioned by Giesbrecht in 1899 in the grouping of this section. TheThaumatoessidaeincludeThaumatoessa(Kröyer), established earlier than its synonymThaumaleus(Kröyer), or thanMonstrilla(Dana, 1849). The species are imperfectly known. The defect of mouth-organs probably does not apply to the period of youth, which some of them spend parasitically in the body-cavity of worms (Giard, 1896). To theCyclopidaesix genera are allotted by Giesbrecht in 1900.Cyclops(O.F. Müller, 1776), though greatly restricted since Müller’s time, still has several scores of species abundantly peopling inland waters of every kind and situation, without one that can be relied on as exclusively marine like the species ofOithona(Baird). TheMisophriidaeare now limited toMisophria(Boeck). The presence of a heart in this genus helps to make it a link between the Podoplea and Gymnoplea, though in various other respects it approaches the next family. TheHarpacticidaeowe their name to the genusArpacticus(Milne-Edwards, 1840). Brady in 1880 assigns to this family 33 genera and 81 species. Canu (1892) distinguishes eight sub-families,Longipediinae,Peltidiinae,Tachidiinae,Amymoninae,Harpacticinae,Idyinae,Canthocamptinae(for whichCanthocampinaeshould be read), andNannopinae, addingStenheliinae(Brady) without distinctive characters for it. TheAscidicolidaehave variable characters, showing a gradual adaptation to parasitic life in Tunicates. Giesbrecht (1900) considers Canu quite right in grouping together in this single family those parasites of ascidians, simple and compound, which had been previously distributed among families with the more or less significant namesNotodelphyidae,Doropygidae,Buproridae,Schizoproctidae,Kossmechtridae,Enterocolidae,Enteropsidae. Further, he includes in it his ownEnterognathus comatulae, not from an ascidian, but from the intestine of the beautiful starfishAntedon rosaceus. TheAsterocheridae, which have a good swimming capacity, except in the case ofCancerilla tubulata(Dalyell), lead a semi-parasitic life on echinoderms, sponges, &c., imbibing their food. Giesbrecht, displacing the older nameAscomyzontidae, assigns to this family 21 genera in five subfamilies, and suggests that the long-known but still puzzlingNicothoëfrom the gills of the lobster might be placed in anadditional subfamily, or be made the representative of a closely related family. TheDichelestiidae, on account of their sometimes many-jointed first antennae, are referred also to this tribe by Giesbrecht. (b) Isokerandria. “Swimming Podoplea without genicullating first antennae in the male sex, and descendants of such. First antennae of male and female almost always articulated alike.” To this tribe Giesbrecht assigns the familiesClausidiidae,Corycaeidae,Oncaeidae,Lichomolgidae,Ergasilidae,Bomolochidae,Clausiidae,Nereicolidae. Here also must for the time be placed theCaligidae,Philichthyidae(Philichthydaeof Vogt, Carus, Claus),Lernaeidae,Chondracanthidae,Sphaeronellidae(better known asChoniostomatidae, from H.J. Hansen’s remarkable study of the group),Lernaeopodidae,Herpyllobiidae,Entomolepidae. For the distinguishing marks of all these, the number of their genera and species, their habits and transformations and dwellings, the reader must be referred to the writings of specialists. Sars (1901) proposed seven suborders—Calanoida, Harpacticoida, Cyclopoida, Notodelphoida, Monstrilloida, Caligoida, Lernaeoida.Authorities.—(The earlier memoirs of importance are cited in Giesbrecht’sMonograph of Naples, 1892); Canu, “Hersiliidae,”Bull. Sci. France belgique, ser. 3, vol. i. p. 402 (1888); andLes Copépodes du Boulonnais(1892); Cuenot,Rev. biol. Nord France, vol. v. (1892); Giesbrecht, “Pelag. Copepoden.”F. u. fl. des Golfes von Neapel(Mon. 19, 1892); Hansen,Entomol. Med.vol. iii. pt. 5 (1892); I.C. Thompson, “Copepoda of Liverpool Bay,”Trans. Liv. Biol. Soc.vol. vii. (1893); Schmeil, “Deutschlands Copepoden,”Bibliotheca zoologica(1892-1897); Brady,Journ. R. Micr. Soc.p. 168 (1894); T. Scott, “Entomostraca from the Gulf of Guinea,”Trans. Linn. Soc. London, vol. vi. pt. 1 (1894); Giesbrecht,Mitteil. Zool. Stat. Neapel, vol. xi. p. 631; vol. xii. p. 217 (1895); T. and A. Scott,Trans. Linn. Soc. London, ser. 2, vol. vi. p. 419 (1896); Hansen “Choniostomatidae” (1897); Sars,Proc. Mus. Zool. St Petersburg, “Caspian Entomostraca” (1897); Giesbrecht and Schmeil, “Copepoda gymnoplea,”Das Tierreich(1898); Giesbrecht, “Asterocheriden,”F. u. fl. Neapel(Mon. 25, 1899); Bassett-Smith, “Copepoda on Fishes,”Proc. Zool. Soc. London, p. 438 (1899); Brady,Trans. Zool. Soc. London, vol. xv. pt. 2, p. 31 (1899); Sars,Arch. Naturv.vol. xxi. No. 2 (1899); Giesbrecht,Mitteil. Zool. Stat. Neapel, vol. xiv. p. 39 (1900); Scott, “Fish Parasites,”Scottish Fishery Board, 18th Ann. Rep. p. 144 (1900); Stebbing,Willey’s Zool. Results, pt. 5, p. 664 (1900); Embleton,Journ. Linn. Soc. London, vol. xxviii. p. 211 (1901); Sars,Crustacea of Norway, vol. iv. (1901).
1.Gymnoplea.—First segment of hind-body footless, bearing the orifices of the genital organs (in the male unsymmetrically placed); last foot of the fore-body in the male a copulatory organ; neither, or only one, of the first pair of antennae in the male geniculating; cephalic limbs abundantly articulated and provided with many plumose setae; heart generally present. Animals usually free-living, pelagic (Giesbrecht and Schmeil).
This group, with 65 genera and four or five hundred species, is divided by Giesbrecht into tribes: (a) Amphaskandria. In this tribe the males have both antennae of the first pair as sensory organs. There is but one family, theCalanidae, but this is a very large one, with 26 genera and more than 100 species. Among them is the cosmopolitanCalanus finmarchicus, the earliest described (by Bishop Gunner in 1770) of all the marine free-swimming Copepoda. Among them also is the peacock Calanid,Calocalanus pavo(Dana), with its highly ornamented antennae and gorgeous tail, the most beautiful species of the whole order (fig. 4). (b) Heterarthrandria. Here the males have one or the other of the first pair of antennae modified into a grasping organ for holding the female. There are four families, theDiaptomidaewith 27 genera, thePontellidaewith 10, thePseudocyclopidaeandCandaciidaeeach with one genus. The first of these families is often calledCentropagidae, but, as Sars has pointed out,Diaptomus(Westwood, 1836) is the oldest genus in it. Of 177 species valid in the family Giesbrecht and Schmeil assign 67 toDiaptomus. In regard to one of its species Dr Brady says: “In one instance, at least (Talkin Tarn, Cumberland) I have seen the net come up from a depth of 6 or 8 ft. below the surface with a dense mass consisting almost entirely ofD. gracilis.” The length of this net-filling species is about a twentieth of an inch.
2.Podoplea.—The first segment of the hind-body almost always with rudimentary pair of feet; orifices of the genital organs (symmetrically placed in both sexes) in the following segment; neither the last foot of the fore-body nor the rudimentary feet just mentioned acting as a copulatory organ in the male; both or neither of the first pair of antennae in the male geniculating; cephalic limbs less abundantly articulated and with fewer plumose setae or none, but with hooks and clasping setae. Heart almost always wanting. Free-living (rarely pelagic) or parasitic (Giesbrecht and Schmeil).
This group is also divided by Giesbrecht into two tribes, Ampharthrandria and Isokerandria. In 1892 he distinguished the former as those in which the first antennae of the male have both members modified for holding the female, and the genital openings of the female have a ventral position, sometimes in close proximity, sometimes strongly lateral; the latter as those in which the first antennae of the male are similar to those of the female, the function of holding her being transferred to the male maxillipeds, while the genital openings of the female are dorsal, though at times strongly lateral. In 1899, with a view to the many modifications exhibited by parasitic and semi-parasitic species, the definitions, stripped of a too hampering precision, took a different form: (a) Ampharthrandria. “Swimming Podoplea with geniculating first antennae in the male sex, and descendants of such; first antennae in female and male almost always differently articulated.” The families occupy fresh water as well as the sea. Naturally “descendants” which have lost the characteristic feature of the definition cannot be recognized without some further assistance than the definition supplies. Of the families comprised, theMormonillidaeconsist only ofMormonilla(Giesbrecht), and are not mentioned by Giesbrecht in 1899 in the grouping of this section. TheThaumatoessidaeincludeThaumatoessa(Kröyer), established earlier than its synonymThaumaleus(Kröyer), or thanMonstrilla(Dana, 1849). The species are imperfectly known. The defect of mouth-organs probably does not apply to the period of youth, which some of them spend parasitically in the body-cavity of worms (Giard, 1896). To theCyclopidaesix genera are allotted by Giesbrecht in 1900.Cyclops(O.F. Müller, 1776), though greatly restricted since Müller’s time, still has several scores of species abundantly peopling inland waters of every kind and situation, without one that can be relied on as exclusively marine like the species ofOithona(Baird). TheMisophriidaeare now limited toMisophria(Boeck). The presence of a heart in this genus helps to make it a link between the Podoplea and Gymnoplea, though in various other respects it approaches the next family. TheHarpacticidaeowe their name to the genusArpacticus(Milne-Edwards, 1840). Brady in 1880 assigns to this family 33 genera and 81 species. Canu (1892) distinguishes eight sub-families,Longipediinae,Peltidiinae,Tachidiinae,Amymoninae,Harpacticinae,Idyinae,Canthocamptinae(for whichCanthocampinaeshould be read), andNannopinae, addingStenheliinae(Brady) without distinctive characters for it. TheAscidicolidaehave variable characters, showing a gradual adaptation to parasitic life in Tunicates. Giesbrecht (1900) considers Canu quite right in grouping together in this single family those parasites of ascidians, simple and compound, which had been previously distributed among families with the more or less significant namesNotodelphyidae,Doropygidae,Buproridae,Schizoproctidae,Kossmechtridae,Enterocolidae,Enteropsidae. Further, he includes in it his ownEnterognathus comatulae, not from an ascidian, but from the intestine of the beautiful starfishAntedon rosaceus. TheAsterocheridae, which have a good swimming capacity, except in the case ofCancerilla tubulata(Dalyell), lead a semi-parasitic life on echinoderms, sponges, &c., imbibing their food. Giesbrecht, displacing the older nameAscomyzontidae, assigns to this family 21 genera in five subfamilies, and suggests that the long-known but still puzzlingNicothoëfrom the gills of the lobster might be placed in anadditional subfamily, or be made the representative of a closely related family. TheDichelestiidae, on account of their sometimes many-jointed first antennae, are referred also to this tribe by Giesbrecht. (b) Isokerandria. “Swimming Podoplea without genicullating first antennae in the male sex, and descendants of such. First antennae of male and female almost always articulated alike.” To this tribe Giesbrecht assigns the familiesClausidiidae,Corycaeidae,Oncaeidae,Lichomolgidae,Ergasilidae,Bomolochidae,Clausiidae,Nereicolidae. Here also must for the time be placed theCaligidae,Philichthyidae(Philichthydaeof Vogt, Carus, Claus),Lernaeidae,Chondracanthidae,Sphaeronellidae(better known asChoniostomatidae, from H.J. Hansen’s remarkable study of the group),Lernaeopodidae,Herpyllobiidae,Entomolepidae. For the distinguishing marks of all these, the number of their genera and species, their habits and transformations and dwellings, the reader must be referred to the writings of specialists. Sars (1901) proposed seven suborders—Calanoida, Harpacticoida, Cyclopoida, Notodelphoida, Monstrilloida, Caligoida, Lernaeoida.
Authorities.—(The earlier memoirs of importance are cited in Giesbrecht’sMonograph of Naples, 1892); Canu, “Hersiliidae,”Bull. Sci. France belgique, ser. 3, vol. i. p. 402 (1888); andLes Copépodes du Boulonnais(1892); Cuenot,Rev. biol. Nord France, vol. v. (1892); Giesbrecht, “Pelag. Copepoden.”F. u. fl. des Golfes von Neapel(Mon. 19, 1892); Hansen,Entomol. Med.vol. iii. pt. 5 (1892); I.C. Thompson, “Copepoda of Liverpool Bay,”Trans. Liv. Biol. Soc.vol. vii. (1893); Schmeil, “Deutschlands Copepoden,”Bibliotheca zoologica(1892-1897); Brady,Journ. R. Micr. Soc.p. 168 (1894); T. Scott, “Entomostraca from the Gulf of Guinea,”Trans. Linn. Soc. London, vol. vi. pt. 1 (1894); Giesbrecht,Mitteil. Zool. Stat. Neapel, vol. xi. p. 631; vol. xii. p. 217 (1895); T. and A. Scott,Trans. Linn. Soc. London, ser. 2, vol. vi. p. 419 (1896); Hansen “Choniostomatidae” (1897); Sars,Proc. Mus. Zool. St Petersburg, “Caspian Entomostraca” (1897); Giesbrecht and Schmeil, “Copepoda gymnoplea,”Das Tierreich(1898); Giesbrecht, “Asterocheriden,”F. u. fl. Neapel(Mon. 25, 1899); Bassett-Smith, “Copepoda on Fishes,”Proc. Zool. Soc. London, p. 438 (1899); Brady,Trans. Zool. Soc. London, vol. xv. pt. 2, p. 31 (1899); Sars,Arch. Naturv.vol. xxi. No. 2 (1899); Giesbrecht,Mitteil. Zool. Stat. Neapel, vol. xiv. p. 39 (1900); Scott, “Fish Parasites,”Scottish Fishery Board, 18th Ann. Rep. p. 144 (1900); Stebbing,Willey’s Zool. Results, pt. 5, p. 664 (1900); Embleton,Journ. Linn. Soc. London, vol. xxviii. p. 211 (1901); Sars,Crustacea of Norway, vol. iv. (1901).
(T. R. R. S.)
ENTRAGUES, CATHERINE HENRIETTE DE BALZAC D’(1579-1633), marquise de Verneuil, mistress of Henry IV., king of France, was the daughter of Charles Balzac d’Entragues and of Marie Touchet, mistress of Charles IX. Ambitious and intriguing, she succeeded in inducing Henry IV. to promise to marry her after the death of Gabrielle d’Estrées, a promise which led to bitter scenes at court when shortly afterwards Henry married Marie de’ Medici. She carried her spite so far as to be deeply compromised in the conspiracy of Marshal Biron against the king in 1606, but escaped with a slight punishment, and in 1608 Henry actually took her back into favour again. She seems then to have been involved in the Spanish intrigues which preceded the death of the king in 1610.
See H. de la Ferrière,Henri IV. le roi, l’amoureux(Paris, 1890).
See H. de la Ferrière,Henri IV. le roi, l’amoureux(Paris, 1890).
ENTRECASTEAUX, JOSEPH-ANTOINE BRUNI D’(1739-1793), French navigator, was born at Aix in 1739. At the age of fifteen he entered the navy. In the war of 1778 he commanded a frigate of thirty-two guns, and by his clever seamanship was successful in convoying a fleet of merchant vessels from Marseilles to the Levant, although they were attacked by two pirate vessels, each of which was larger than his own ship. In 1785 he was appointed to the command of the French fleet in the East Indies, and two years later he was named governor of the Mauritius and the Isle of Bourbon. While in command of the East India fleet he made a voyage to China, an achievement which, in 1791, led the French government to select him to command an expedition which it was sending out to seek some tidings of the unfortunate La Pérouse, of whom nothing had been heard since February 1788. Rear-admiral d’Entrecasteaux’s expedition comprised the “Recherche” and “L’Esperance,” with Captain Huon de Kermadec as second in command. No tidings were obtained of the missing navigator, but in the course of his search Entrecasteaux made important geographical discoveries. He traced the outlines of the eastern coast of New Caledonia, made extensive surveys round the Tasmanian coast, and touched at several places on the south coast of New Holland. The two ships entered Storm Bay, Tasmania, on the 21st of April 1792, and remained there until the 16th of May, surveying and naming the d’Entrecasteaux Channel, the entrances to the Huon and Derwent rivers, Bruni Island, Recherche Bay, Port Esperance and various other localities. Excepting the name of the river Derwent (originally called Riviere du Nord by its French discoverers), these foregoing appellations have been retained. Leaving Tasmania the expedition sailed northward for the East Indies, and while coasting near the island of Java, Entrecasteaux was attacked by scurvy and died on the 20th of July 1793.
ENTRE MINHO E DOURO(popularly calledMinho), a former province of Northern Portugal; bounded on the N. by Galicia in Spain, E. by Traz-os-Montes, S. by Beira and W. by the Atlantic Ocean. Pop. (1900) 1,170,361; area 2790 sq. m. Though no longer officially recognized, the old provincial name remains in common use. The coast-line of Entre Minho e Douro is level and unbroken except by the estuaries of the main rivers; inland, the elevation gradually increases towards the north and east, where several mountain ranges mark the frontier. Of these, the most important are the Serra da Peneda (4728 ft.), between the rivers Minho and Limia; the Serra do Gerez (4357 ft.), on the Galician border; the Serra da Cabreira (4021 ft.), immediately to the south; and the Serra de Marão (4642 ft.), in the extreme south-east. As its name implies, the province is bounded by two great rivers, the Douro (q.v.) on the south, and the Minho (SpanishMiño) on the north; but a small tract of land south of the Douro estuary is included also within the provincial boundary. There are three other large rivers which, like the Minho, flow west-south-west into the Atlantic. The Limia or Antela (SpanishLinia) rises in Galicia, and reaches the sea at Vianna do Castello; the Cavado springs from the southern foot hills of La Raya Seca, on the northern frontier of Traz-os-Montes, and forms, at its mouth, the small harbour of Espozende; and the Ave descends from its sources in the Serra da Cabreira to Villa do Conde, where it enters the Atlantic. A large right-hand tributary of the Douro, the Tamega, rises in Galicia, and skirts the western slopes of the Serra de Marão.
The climate is mild, except among the mountains, and such plants as heliotrope, fuchsias, palms, and aloes thrive in the open throughout the year. Wheat and maize are grown on the plains, and other important products are wine, fruit, olives and chestnuts. Fish abound along the coast and in the main rivers; timber is obtained from the mountain forests, and dairy-farming and the breeding of pigs and cattle are carried on in all parts. As the province is occupied by a hardy and industrious peasantry, and the density of population (419.5 per sq. m.) is more than twice that of any other province on the Portuguese mainland, the soil is very closely cultivated. The methods and implements of the farmers are, however, most primitive, and at the beginning of the 20th centuryitwas not unusual to see a mule, or even a woman, harnessed with the team of oxen to an old-fashioned wooden plough. Small quantities of coal, iron, antimony, lead and gold are mined; granite and slate are quarried; and there are mineral springs at Monção (pop. 2283) on the Minho. The Oporto-Corunna railway traverses the western districts and crosses the Spanish frontier at Tuy; its branch lines give access to Braga, Guimarães and Povoa de Varzim; and the Oporto-Salamanca railway passes up the Douro valley. The greater part of the north and west can only be reached by road, and even the chief highways are ill-kept. In these regions the principal means of transport is the springless wooden cart, drawn by one or more of the tawny and under-sized but powerful oxen, with immense horns and elaborately carved yoke, which are characteristic of northern Portugal. For administrative purposes the province is divided into three districts: Vianna do Castello in the north, Braga in the centre, Oporto in the south. The chief towns are separately described; they include Oporto (167,955), one of the greatest wine-producing cities in the world; Braga (24,202), the seat of an archbishop who is primate of Portugal; the seaports of Povoa de Varzim (12,623) and Vianna do Castello (9990); and Guimarães (9104), a place of considerable historical interest.
ENTREPÔT(a French word, from the Lat.interpositum, that which is placed between), a storehouse or magazine for the temporary storage of goods, provisions, &c.; also a place where goods, which are not allowed to pass into a country duty free, are stored under the superintendence of the custom house authorities till they are re-exported. In a looser sense, any town which has a considerable distributive trade is called anentrepôt. The word is also used attributively to indicate the kind of trade carried on in such towns.
ENTRE RIOS(Span. “between rivers”), a province of the eastern Argentine Republic, forming thesouthernpart of a region sometimes described as the Argentine Mesopotamia, bounded N. by Corrientes, E. by Uruguay with the Uruguay river as the boundary line, S. by Buenos Aires and W. by Santa Fé, the Paraná river forming the boundary line with these two provinces. Pop. (1895) 292,019; (1905, est.) 376,600. The province has an area of 28,784 sq. m., consisting for the most part of an undulating, well-watered and partly-wooded plain, terminating in a low, swampy district of limited extent in the angle between the two great rivers. The great forest of Monteil occupies an extensive region in the N., estimated at nearly one-fifth the area of the province. Its soil is exceptionally fertile and its climate is mild and healthy. The province is sometimes called the “garden of Argentina,” which would probably be sufficiently correct had its population devoted as much energy to agriculture as they have to political conflict and civil war. Its principal industry is that of stock-raising, exporting live cattle, horses, hides, jerked beef, tinned and salted meats, beef extract, mutton and wool. Its agricultural products are also important, including wheat, Indian corn, barley and fruits. Lime, gypsum and firewood are also profitable items in its export trade. The Paraná and Uruguay rivers provide exceptional facilities for the shipment of produce and the Entre Rios railways, consisting of a trunk line running E. and W. across the province from Paraná to Concepción del Uruguay and several tributary branches, afford ample transportation facilities to the ports. Another railway line follows the Uruguay from Concordia northward into Corrientes. Entre Rios has been one of the most turbulent of the Argentine provinces, and has suffered severely from political disorder and civil war. Comparative quiet reigned from 1842 to 1870 under the autocratic rule of Gen. J.J. Urquiza. After his assassination in 1870 these partizan conflicts were renewed for two or three years, and then the province settled down to a life of comparative peace, followed by an extraordinary development in her pastoral and agricultural industries. Among these is the slaughtering and packing of beef, the exportation of which has reached large proportions. The capital is Paraná, though the seat of government was originally located at Concepción del Uruguay, and was again transferred to that town during Urquiza’s domination. Concepción del Uruguay, or Concepción (founded 1778), is a flourishing town and port on the Uruguay, connected by railway with an extensive producing region which gives it an important export trade, and is the seat of a national college and normal school. Its population was estimated at 9000 in 1905. Other large towns are Gualeguay and Gualeguaychú.
ENVOY(Fr.envoyé, “sent”), a diplomatic agent of the second rank. The wordenvoyécomes first into general use in this connexion in the 17th century, as a translation of the Lat.ablegatusormissus(seeDiplomacy). Hence the word envoy is commonly used of any one sent on a mission of any sort.
ENZIO(c.1220-1272), king of Sardinia, was a natural son of the emperor Frederick II. His mother was probably a German, and his name, Enzio, is a diminutive form of the GermanHeinrich. His father had a great affection for him, and he was probably present at the battle of Cortenuova in 1237. In 1238 he was married, in defiance of the wishes of Pope Gregory IX., to Adelasia, widow of Ubaldo Visconti and heiress of Torres and Gallura in Sardinia. Enzio took at once the title of king of Torres and Gallura, and in 1243 that of king of Sardinia, but he only spent a few months in the island, and his sovereignty existed in name alone. In July 1239 he was appointed imperial vicegerent in Italy, and sharing in his father’s excommunication in the same year, took a prominent part in the war which broke out between the emperor and the pope. He commenced his campaign by subduing the march of Ancona, and in May 1241 was in command of the forces which defeated the Genoese fleet at Meloria, where he seized a large amount of booty and captured a number of ecclesiastics who were proceeding to a council summoned by Gregory to Rome. Later he fought in Lombardy. In 1248 he assisted Frederick in his vain attempt to take Parma, but was wounded and taken prisoner by the Bolognese at Fossalta on the 26th of May 1249. His captivity was a severe blow to the Hohenstaufen cause in Italy, and was soon followed by the death of the emperor. He seems to have been well treated by the people of Bologna, where he remained a captive until his death on the 14th of March 1272. He was apparently granted a magnificent funeral, and was buried in the church of St Dominic at Bologna. During his imprisonment Enzio is said to have been loved by Lucia da Viadagola, a well-born lady of Bologna, who shared his captivity and attempted to procure his release. Some doubt has, however, been cast upon this story, and the same remark applies to another which tells how two friends had almost succeeded in freeing him from prison concealed in a wine-cask, when he was recognized by a lock of his golden hair. His marriage with Adelasia had been declared void by the pope in 1243, and he left one legitimate, and probably two illegitimate daughters. Enzio forms the subject of a drama by E.B.S. Raupach and of an opera by A.F.B. Dulk.