Plumatella diffusa, Leidy, P. Ac. Philad. v, p. 261 (1852).Plumatella diffusa, Allman, Mon. Fresh-Water Polyzoa, p. 105 (1857).Plumatella diffusa, Hyatt, Comm. Essex Inst. iv, pl. viii, figs. 11, 12 (1866).Plumatella diffusa,id.,ibid.v, p. 107, fig. 12 (1868).Plumatella repens, Jullien, Bull. Soc. zool. France, x, fig. 37 (lapsusfor 73), p. 110 (1885).Plumatella diffusa,id.,ibid.figs. 155, 157, pp. 130, 131.Plumatella allmanivar.diffusa, Annandale, Rec. Ind. Mus. v, p. 49 (1910).
Zoarium.The zoarium often covers a considerable area on flat surfaces and is sometimes found crowded together on the stems of plants. In the latter case the arrangement of the main branches is distinctly radiate. Upright branches occur rarely and never consist of more than three zoœcia. The characteristic method of branching is best represented by the following diagram:—
Illustration: Fig. 43.Fig. 43.
Fig. 43.
The partitions are stout and numerous.
Zoœcia.The great majority of the zoœcia in each zoarium are distinctlyL-shaped, the long limb being usually adherent. The vital organs of the polypide are contained in the vertical limb, while the horizontal one, in mature polyparia, is packed full of free statoblasts. The zoœcia are cylindrical and as a rule obscurely emarginate and furrowed. The ectocyst is stiff; it is never deeply pigmented but is usually of a transparent horn-colour at the base of each zoœcium and colourless at the tip, the contrast between the two portions never being very strong. The basal portion is rough on the surface, the distal portion smooth.
Statoblasts.Free statoblasts are produced in very great profusion and fixed statoblasts are also to be found as a rule. The latter resemble those ofP. emarginata. The free statoblasts are never very large or relatively broad, but they vary considerably as regards size and outline. The capsule is large, the sides convex outwards and the extremity more or less broadly rounded. The air-cells are unusually large and extend over a great part of the dorsal surface of the statoblast.
Polypide.The polypide is shorter and stouter than that ofP. emarginataand as a rule has fewer tentacles.
The most characteristic feature of this species is the form of the zoœcia, which differ greatly from those of any other Indian species butP. allmani. In the latter they are distinctly "keg-shaped" (i. e., constricted at the base and swollen in the middle), and the zoarium never spreads out over large surfaces in the way in which that ofP. diffusadoes.
Type—? in the Philadelphia Academy of Sciences.
Geographical Distribution.—This species was originally described from North America (in which it is apparently common) and occurs also in Europe. I have seen Indian specimens from the following localities:—Bengal, Calcutta and neighbourhood; Rajshahi (Rampur Bhulia):E. Himalayas, Gangtok, Native Sikhim (alt. 6,150 feet) (Kirkpatrick,Stewart):Punjab, Lahore (Stephenson).
Biology.—P. diffusain Lower Bengal is a cold-weather species. It is remarkable for the enormous number of gemmules it produces and is usually found either on floating objects such as the stems of certain water-plants, or on stones or bricks at the edge of ponds.
33.Plumatella allmani,Hancock. (Plate IV, figs. 3, 3a.)
Plumatella allmani, Hancock, Ann. Nat. Hist. (2) v, p. 200, pl. v, fig. 3-4, pl. iii, fig. 2-3 (1850).Plumatella allmani, Allman, Mon. Fresh-Water Polyzoa, p. 106, fig. 16 (1857).Plumatella elegans,id.,ibid.p. 107, pl. viii, figs. 6-10.Plumatella lucifuga("forme rampante") Jullien, Bull. Soc. zool. France, x, p. 114 (1885).
This species is closely allied toP. diffusa, from which it differs in the following characters:—
(1) The zoarium never covers a large area and as a rule grows sparingly and mainly in two directions.
(2) The zoœcia are more irregular in shape, not so distinctly elbowed, smaller; they have a much more prominently keeled ridge. The great majority of them are constricted at the base and taper towards the orifice. In young zoaria they are almost colourless but in older ones there is a band of not very dense pigment round the base of the vertical limb.
(3) The free statoblasts are comparatively large and usually show a tendency to taper at the extremities, often being almost rhomboidal in form. The swim-ring does not extend so far over the dorsal surface as it does in those ofP. diffusa; the "cells" of which it is composed are small.
Typenot in existence.
I have seen every gradation between this form and Allman'sP. elegans.
Geographical Distribution.—P. allmaniis apparently a rare species to which there are few references in literature. It was originally described from England and is stated by Jullien to occur in France. I have found specimens only in the lake Bhim Tal (alt. 4,500 feet) in the W. Himalayas.
Biology.—The original specimens were found by Hancock on stones. My own were growing on the leaves of water-plants, usually on the under side. When the zoœcia were forced to stretch across from one leaflet to another they assumed the sinuous form characteristic of Allman'sP. elegans.
34.Plumatella tanganyikæ,Rousselet.
Plumatella tanganyikæ, Rousselet, Proc. Zool. Soc. London, 1907 (i), p. 252, pl. xiv, figs. 1-4.Plumatella bombayensis, Annandale, Rec. Ind. Mus. ii, p. 169, figs. 1, 2 (1908).Plumatella bombayensis,id.,ibid.v, p. 51 (1910).
Zoarium.The whole colony is recumbent but branches freely and at short intervals in a horizontal plane, so that the zoœcia become crowded together and the branches sometimes overlap one another. The zoarium often covers a considerable area, but growth seems to be mainly in two directions. When growing on the stems of water-plants the branches are often parallel and closely pressed together but remain recumbent in this position. A stout membrane sometimes extends between branches and individual zoœcia.
Zoœcia.The walls of the zoœcia are thick, stiff, and more or less darkly but not opaquely pigmented; the external surface, although not very smooth, is always clean. The two most noteworthy characters of the zoœcia are (i) their truncated appearance when the polypide is retracted, and (ii) the conspicuous, although often irregular external annulation of their walls. The tip of each zoœcium, owing to the fact that the invaginated part of the ectocyst is soft and sharply separated from the stiffened wall of the tube, terminates abruptly and is not rounded off gradually as is the case in most species of the genus; sometimes it expands into a trumpet-like mouth. The annulation of the external surface is due to numerous thickened areas of the ectocyst which take the form of slender rings surrounding the zoœcium; they are most conspicuous on its distal half. On the dorsal surface of the base of each zoœcium there is a conspicuous furrowed keel, which, however, does not usually extend to the distal end; the latter is oval in cross-section. The zoœcia are short and broad; their base is always recumbent, and, when the zoarium is attached to a stone or shell, often seems to be actually embedded in the support; the distal part turns upwards and is free, so that the aperture is terminal; the zoœcia of the older parts of the zoariumexhibit the specific characters much more clearly than those at the growing points.
Polypide.The lophophore bears 20 to 30 tentacles, which are long and slender; the velum at their base extends up each tentacle in the form of a sharply pointed projection, but these projections do not extend for more than one-fifth of the length of the tentacles. Both the velum and the tentacular sheath bear numerous minute tubercles on the external surface. The base of the stomach is rounded, and the whole of the alimentary canal has a stout appearance.
Illustration: Fig. 44.—Plumatella tanganyikæ from Igatpuri Lake.Fig. 44.—Plumatella tanganyikæfrom Igatpuri Lake.
Fig. 44.—Plumatella tanganyikæfrom Igatpuri Lake.
A=outline of part of zoarium from a stone, × 16; B=outline of the tip of a single zoœcium, × 70; C=free statoblast, × 70.
Statoblasts.Both fixed and free statoblasts are produced, but not in very large numbers. The latter are broadly oval and are surrounded by a stout chitinous ring, which often possesses irregular membranous projections; the surface is smooth. The free statoblasts are small and moderately elongate, the maximum breadth as a rule measuring about 2/3 of the length; the capsule is relatively large and the ring of air-cells is not very much broader at the ends than at the sides; the dorsal surface of the central capsule is profusely tuberculate. The outline of the whole structure is often somewhat irregular.
In deference to Mr. Rousselet's opinion expressed in a letter I have hitherto regarded the Bombay form of this species as distinct from the African one, and there certainly is a great difference in the appearance of specimens taken on the lower surface of stones in Igatpuri Lake and of the types ofP. tanganyikæ, one of which is now in the collection of the Indian Museum. The dark colour of the former, however, and their vigorous growth appear to be directly due to environment, for these characters disappear to a large extent in specimens growing on the stems of water-plants in the same lake. Indeed, such specimens are exactly intermediate between the form "bombayensis" and the typical form of the species.P. tanganyikæis closely allied toP. philippinensis, Kraepelin, from the island of Luzon, but the latter has a smooth and polished ectocyst devoid of annulations, and zoœcia of a more elongate and regular form.
Typesof the species in the British and Indian Museums, those ofP. bombayensisin the latter collection.
Geographical Distribution.—P. tanganyikæis only known as yet from L. Tanganyika in Central Africa and from Igatpuri in the Bombay Presidency.
Biology.—In both localities the zoaria were found in shallow water. In L. Tanganyika they were encrusting stones and shells, while at Igatpuri they were fixed for the most part to the lower surface of stones but were also found on the stems of water-plants. My specimens from the Bombay Presidency were taken, on two separate occasions, at the end of November. At that date the zoaria were already decaying and large blanks, marked out by fixed statoblasts, were often observed on the stones. Probably, therefore, the species flourishes during the "rains."
35.Plumatella punctata,Hancock. (Plate IV, fig. 5.)
Plumatella punctata, Hancock, Ann. Nat. Hist. (2) v, p. 200, pl. iii, fig. 1, and pl. v, figs. 6, 7 (1850).Plumatella vesicularis, Leidy, P. Ac. Philad. vii, p. 192 (1854).Plumatella vitrea, Hyatt, Comm. Essex Inst. iv, pl. ix, figs. 1, 2 (1866).Plumatella punctata, Allman, Mon. Fresh-Water Polyzoa, p. 100, fig. 15 (1857).Plumatella vesicularis,id.,ibid.p. 101.Plumatella vitrea, Hyatt, Proc. Essex Inst. v, p. 225, figs. 18, 19 (1868).Plumatella vesicularis,id.,ibid.p. 225.Hyalinella vesicularis, Jullien, Bull. Soc. zool. France, x, p. 133, figs. 165-172 (1885).Hyalinella vitrea,id.,ibid.p. 134, figs. 173-179.Plumatella punctata, Kraepelin, Deutsch. Süsswasserbryozoen, i, p. 126, pl. iv, figs. 115, 116; pl. v, figs. 124, 125; pl. vii, figs. 153, 154 (1887).Plumatella vesicularis, Braem, Unters. ü. Bryozoen süssen Wassers, p. 8, pl. i, fig. 8 (Bibl. Zool. ii) (1890).Hyalinella punctata, Loppens, Ann. Biol. lacustre, iii, p. 163 (1908).Plumatella punctata, Annandale, Rec. Ind. Mus. v, p. 52 (1910).
Zoarium.The zoarium is entirely recumbent and often appears to form an almost uniform flat layer instead of a dendritic body. Sometimes, however, it is distinctly linear, with lateral branches produced irregularly at considerable distances apart.
Zoœcia.The zoœcia differ from those of all other species in having a greatly swollen, soft ectocyst which can be transversely wrinkled all over the zoœcium by the action of the muscles of the polypide and is distinctly contractile. It is mainly owing to the swollen and almost gelatinous nature of the ectocyst that the dendritic character of the zoarium is frequently concealed, for the method of branching is essentially the same as that ofP. diffusa, although the zoœcia are not so distinctly elbowed. The ectocyst is colourless or faintly tinted with brown; as a rule it is not quite hyaline and the external surface is minutely roughened or tuberculate. The zoœcia are not emarginate or furrowed.
Statoblasts.Stationary statoblasts are not found. The free statoblasts are variable and often asymmetrical in outline, but the free portion of the swim-ring is always of nearly equal diameter all round the periphery and the capsule relatively large. Some of the statoblasts are always broad in comparison with their length.
Polypide.The polypide is comparatively short and stout. European specimens are said to have from 30 to 40 tentacles, but Indian specimens have only from 20 to 30.
Shrunken specimens of the less congested forms of this species closely resemble specimens ofP. repens, but the statoblasts are more variable in shape and the ectocyst, even in such specimens, is thicker. Living or well-preserved specimens cannot be mistaken for those of any other species. Jullien regardedP. punctataas the type of a distinct genus (Hyalinella) but included inPlumatellaat least one form (P. "arethusa") which probably belongs to this species. Kraepelin distinguishes as "varieties" two phases, a summer phase ("var.prostrata") and an autumn phase ("var.densa"). The former often forms linear series of considerable length with only an occasional side-branch, while in the autumn phase branching is so profuse and the branches are so closely pressed together that the zoarium comes to resemble a uniform gelatinous patch rather than a dendritic growth. Aphase resembling the European autumn form is the commonest in Calcutta and I have also found one intermediate between this and Kraepelin's "var.prostrata," neither having any seasonal significance in India.
Geographical Distribution.—P. punctatais widely distributed in Europe and N. America, but in the Oriental Region it has only been found in Calcutta and the neighbourhood.
Biology.—In this part of IndiaP. punctataflourishes both during the "rains" and in winter. I have found specimens in June and July and also in December and January. The majority of them were attached to bricks, but some were on the roots of duckweed, the stems of water-plants, and the tips of creepers falling into water. The species is often found together withStolella indicaand also with other species of its own genus. It is most common, in the neighbourhood of Calcutta, in that part of the town which is near the Salt Lakes, and occurs in ponds the water of which is slightly brackish.
Genus 2.STOLELLA,Annandale.
Stolella, Annandale, Rec. Ind. Mus. iii, p. 279 (1909).Stolella,id.,ibid.v, p. 53 (1910).
Type,Stolella indica, Annandale.
Zoarium. The zoarium consists of groups of zoœcia (or occasionally of single zoœcia) joined together by an adherent rhizome. There is no gelatinous investment.
Zoœcia.The adult zoœcia resemble those ofPlumatellaexcept in being sometimes more or less upright.
PolypideandStatoblasts.The polypide and statoblasts resemble those ofPlumatella. Fixed as well as free statoblasts occur.
This genus is closely allied toPlumatella, from which it is probably derived. The root-like tube from which the zoœcia arise is formed by the great elongation of the basal part of a zoœcium, and the zoaria closely resemble those ofP. punctata, for it is not until several zoœcia have been produced that the characteristic mode of growth becomes apparent.
Stolellahas only been found in India and is monotypic[BJ].
36.Stolella indica,Annandale. (Plate V, figs. 3, 4.)
Stolella indica, Annandale, Rec. Ind. Mus. iii, p. 279, fig. (1909).Stolella indica,id.,ibid.v, p. 53 (1910).
Zoarium.The zoarium is adherent and linear, having neither lateral nor vertical branches.
Zoœcia.The zoœcia are short and slender, erect or nearly so, distinctly emarginate and furrowed. Their ectocyst is soft, colourless and transparent but minutely roughened on the surface.
Polypide.The tentacles number from 30 to 35 and are rather short and stout, sometimes being slightly expanded at the tips. The stomach is comparatively short and abruptly truncated posteriorly.
Statoblasts.Both free and fixed statoblasts are found, and both are variable in form, the latter varying in outline from the circular to the broadly oval. The free statoblasts resemble those ofPlumatella punctata, but are sometimes rather more elongate.
Typein the Indian Museum.
Illustration: Fig. 45.—Zoarium of Stolella indica on stem of water-plant (from Calcutta), × 6.Fig. 45.—Zoarium ofStolella indicaon stem of water-plant (from Calcutta), × 6.
Fig. 45.—Zoarium ofStolella indicaon stem of water-plant (from Calcutta), × 6.
Geographical Distribution.—So far as we know, this species is confined to the Indo-Gangetic Plain. Major Walton found it at Bulandshahr in the United Provinces, and it is not uncommon in the neighbourhood of Calcutta.
Biology.—The zoaria ofS. indicaare usually fixed to the roots of duckweed or to the stems of other plants. They are often found together with those ofP. punctata. A slight infusion of brackish water into the ponds in which it lives does not seem to be inimical to this species, but I have found it in ponds in which nothing of the kind was possible. It flourishes during the "rains" and, to judge from specimens kept in an aquarium, is very short-lived. Major Walton found it growing over a zoarium ofHislopia lacustris.
Subfamily B. LOPHOPINÆ.
The zoaria of this subfamily are never dendritic but form gelatinous masses which, except inAustralella, are cushion-shaped or sack-like. With the possible exception ofAustralella, they possess to a limited extent the power of moving along vertical or horizontal surfaces, but it is by no means clear how they do so (see p. 172). The statoblasts are remarkable for their large size, and it is noteworthy thatAustralella, which is intermediate in structure between the Plumatellinæ and the Lophopinæ, possesses statoblasts of intermediate size. The swim-ring is always well developed, and fixed statoblasts are unknown.
Only two genera (LophopodellaandPectinatella) have been definitely proved to occur in India, but a third (Lophopus[BK]) is stated to have been found in Madras. Should it be met with it will easily be recognized by the upright position of its polypides when their tentacles are expanded and by the fact that the statoblasts never bear marginal processes.
Genus 3.LOPHOPODELLA,Rousselet.
Lophopodella, Rousselet, Journ. Quek. Micr. Club (2) ix, p. 45 (1904).Lophopodella, Annandale, Rec. Ind. Mus. v, p. 54 (1910).
Type,Pectinatella carteri, Hyatt.
Zoarium.The zoarium consists of a circular or oval mass of no great size. Polyparia do not form compound colonies.
Polypides.The polypides lie semi-recumbent in the mass and never stand upright in a vertical position.
Statoblasts.The statoblasts are of considerable size and normally bear at both ends a series of chitinous processes armed with double rows of small curved spinules.
As a rule the genus is easily recognized by means of the statoblasts, but sometimes the processes at the ends of these structures are absent or abortive and it is then difficult to distinguish them from those ofLophopus. There is, however, no species of thatgenus known that has statoblasts shaped like those of the Indian species ofLophopodella.
Three species ofLophopodella, all of which occur in Africa, have been described;L. capensisfrom S. Africa, which has the ends of the statoblast greatly produced,L. thomasifrom Rhodesia, in which they are distinctly concave, andL. carterifrom E. Africa, India and Japan, in which they are convex or truncate.
The germination of the gemmule and the early stages in the development of the polyparium ofL. capensishave been described by Miss Sollas (Ann. Nat. Hist. (8) ii, p. 264, 1908).
37.Lophopodella carteri(Hyatt). (Plate III, figs. 4, 4a.)
Lophopussp., Carter, Ann. Nat. Hist. (3) iii, p. 335, pl. viii, figs. 8-15 (1859).?Lophopussp., Mitchell, Q. J. Micr. Sci. London (3) ii, p. 61 (1862).Pectinatella carteri, Hyatt, Comm. Essex Inst. iv, p. 203 (footnote) (1866).Pectinatella carteri, Meissner, Die Moosthiere Ost-Afrikas, p. 4 (in Mobius's Deutsch-Ost-Afrika, iv, 1898).Lophopodella carteri, Rousselet, Journ. Quek. Micr. Club, (2) ix, p. 47, pl. iii, figs. 6, 7 (1904).Lophopus carteri, Annandale, Rec. Ind. Mus. ii, p. 171, fig. 3 (1908).Lophopodella carteri,id.,ibid.v, p. 55 (1910).
Zoarium.The zoarium as a rule has one horizontal axis longer than the other so that it assumes an oval form when the polypides are expanded; when they are retracted its outline is distinctly lobular. Viewed from the side it is mound-shaped. The polypides radiate, as a rule in several circles, from a common centre. The ectocyst is much swollen, hyaline and colourless.
Polypide.The polypide has normally about 60 tentacles, the velum at the base of which is narrow and by no means strongly festooned. The stomach is yellow or greenish in colour. The extended part of the polypide measures when fully expanded rather less than 3 mm., and each limb of the lophophore about the same.
Statoblast.The statoblast is variable in shape and size but measures on an average about 0.85 × 0.56 mm. The ends are truncate or subtruncate; the capsule is small as compared with the swim-ring and as a rule circular or nearly so. The processes at the two ends are variable in number; so also are their spinules, which are arranged in two parallel rows, one row on each side of the process, and are neither very numerous nor set close together; as a rule they curve round through the greater part of a circle and are absent from the basal part of the process.
Illustration: Fig. 46.—Lophopodella carteri (from Igatpuri Lake).Fig. 46.—Lophopodella carteri (from Igatpuri Lake).
Fig. 46.—Lophopodella carteri (from Igatpuri Lake).
A=outline of a zoarium with the polypides expanded, as seen from below through glass to which it was attached, × 4; B=outline of a zoarium with the polypides highly contracted, as seen from above, × 4; C=statoblast, × 75.
37a.Var.himalayana.
Lophopus lendenfeldi, Annandale (necRidley), J. As. Soc. Bengal, (n. s.) iii, 1907, p. 92, pl. ii, figs. 1-4 (1907).Lophopus lendenfeldivar.himalayanus,id., Rec. Ind. Mus. i, p. 147, figs. 1, 2 (1907).Lophopus himalayanus,id.,ibid.ii, p. 172, fig. 4 (1908).
This variety differs from the typical form in having fewer tentacles and in the fact that the marginal processes of the statoblast are abortive or absent.
Pectinatella davenporti, Oka[BL]from Japan is evidently a local race ofL. carteri, from the typical form of which it differs in having the marginal processes of the statoblast more numerous and better developed. The abortive structure of these processes in var.himalayanapoints to an arrest of development, for they are the last part of the statoblast to be formed.
Types.The statoblasts mounted in Canada balsam by Carter and now in the British Museum must be regarded as the types of the species named but not seen by Hyatt. The types of the var.himalayanaare in the Indian Museum and those of the subspeciesdavenportipresumably in the possession of Dr. Oka in Tokyo.
Geographical Distribution.—The typical form occurs in Bombay, the W. Himalayas and possibly Madras, and its statoblasts have been found in E. Africa; the var.himalayanahas only been taken in the W. Himalayas and the subspeciesdavenportiin Japan. Indian localities are:—Bombay Presidency, Igatpuri Lake, W. Ghats (alt.ca.2,000 feet); the Island of Bombay (Carter):W. Himalayas, Bhim Tal, Kumaon (alt. 4,500 feet).
Biology.—L. carteriis found on the lower surface of stones and on the stems and leaves of water-plants, usually in lakes or large ponds. Although the zoaria do not form compound colonies by secreting a common membrane or investment, they are markedly gregarious. The most closely congregated and the largest zoaria I have seen were assembled amongst a gelatinous green alga of the genusTolypothrix[BM](Myxophyceæ) that grows on the vertical stems of a plant at the edge of Igatpuri Lake; it is noteworthy that in this case the alga seemed to take the place of the common investment ofPectinatella burmanica, in which green cells are present in large numbers (p. 237). The zoaria ofL. carteriare able to change their position, and I found that if a number of them were placed in a bottle of water they slowly came together at one spot, thus apparently forming temporary compound colonies. Before a movement of the whole zoarium commences its base becomes detached from its support at the anterior end (fig. 32, p. 172), but the whole action is extremely slow and I have not been able to discover any facts that cast light on its exact method of production. At Igatpuri statoblasts are being produced in considerable numbers at the end of November, but many young zoaria can be found in which none have as yet been formed.
The larva of a fly of the genusChironomusis often found inhabiting a tube below zoaria ofL. carteri. It is thus protected from its enemies but can protrude its head from beneath the zoarium and seize the small animals on which it preys.
Genus 4.PECTINATELLA,Leidy.
Cristatella, Leidy, P. Ac. Philad. v, p. 265 (1852).Pectinatella,id.,ibid., p. 320.Pectinatella, Allman, Mon. Fresh-Water Polyzoa, p. 81 (1857).Pectinatella, Hyatt, Proc. Essex Inst. v, p. 227, fig. 20 (1867).Pectinatella, Kraepelin, Deutsch. Süsswasserbryozoen, i, p. 133 (1887).Pectinatella, Oka, Journ. Coll. Sci. Tokyo, iv, p. 89 (1891).
Type,Pectinatella magnifica, Leidy.
This genus is closely allied toLophopodella, from which it is often difficult to distinguish young specimens. Adult zoaria are, however, always embedded together in groups in a gelatinous investment which they are thought to secrete in common[BN], and the statoblasts are entirely surrounded by processes that bear curved spinules at their tips only. The polypides have the same semi-recumbent position as those ofLophopodellabut are larger than those of any species ofLophopodellaorLophopusyet known. The statoblasts are larger than those of any other Plumatellidæ.
The type-species was originally found in N. America but has since been taken in several localities in continental Europe. Except this and the Indian form only one species is known, namelyP. gelatinosafrom Japan.P. magnificahas circular statoblasts with long marginal processes, while inP. gelatinosathe statoblasts are subquadrate and inP. burmanicaalmost circular, both Asiatic forms having very short marginal processes.
The compound colonies formed byPectinatellaare often of great size. Those ofP. gelatinosaare sometimes over 2 metres in length, while those ofP. burmanicain the Sur Lake appeared to be only limited as regards their growth by the shallowness of the water in which the reeds to which they were attached were growing. Some were observed that were over 2 feet long.
38.Pectinatella burmanica,Annandale. (Plate III, fig. 5.)
Pectinatella burmanica, Annandale, Rec. Ind. Mus. ii, p. 174, fig. 5 (1908).Pectinatella burmanica,id.,ibid.v, p. 56 (1910).Pectinatella burmanica,id., Spol. Zeyl. vii, p. 63, pl. i, fig. 3 (1910).
Zoarium.The zoaria are circular or nearly so except when about to undergo division, in which case they are constricted in the middle. As a rule they measure nearly an inch (2 cm.) indiameter. The polypides have a definite arrangement in each zoarium, being divided into four groups, each of which has a fan-like form. In the first place they are separated into two main divisions in a line running through the centre of the zoarium, and secondly each main division is separated into two subordinate ones in a line running across the other at right angles. The number of zoaria joined together in a single compound colony is very variable; sometimes there are only about half a dozen and sometimes several hundreds. The common investment in living colonies is often as much as two inches thick and has a translucent dark greenish colour due to the presence in it of green cells.
Illustration: Fig. 47.—Pectinatella burmanica.Fig. 47.—Pectinatella burmanica.
Fig. 47.—Pectinatella burmanica.
A=polypide with the lophophore expanded, × 15;a=œsophagus;b=cardiac limb of stomach;c=stomach;d=rectum;e=anus;f=funiculus. [The muscles are omitted and the external tubercles are only shown on part of the polypide. The specimen is from the Sur Lake, Orissa.] B=statoblast from Ceylon, × 35.
Polypide.The polypide can be extruded for a distance of at least 5 mm. Its whole external surface is covered with minute tubercles. There are about 90 tentacles, which are long and slender, the velum at their base being narrow and almost straight. The stomach is of considerable stoutness.
Statoblast.The statoblasts are of large size, measuring from 1 to 1.75 mm. in diameter. In form they are almost circular, but one side is always slightly flattened. The marginal processes are veryshort and bear a single pair of hooks at the tip. The capsule is circular and small as compared with the free part of the swim-ring.
Typein the Indian Museum.
P. burmanicais evidently a near relation ofP. gelatinosa, Oka, from Japan, differing from that species in the shape of the statoblasts and in having much longer tentacles. The arrangement of the polypides in the zoarium and the general structure of the statoblasts are very similar in the two species.
Geographical Distribution.—P. burmanicawas originally described from a swamp at Kawkareik in the Amherst district of Tenasserim but has also been found in the Sur Lake near Puri in Orissa. Dr. A. Willey obtained specimens from a pool by the roadside between Maradankadewela and Galapitagala, at the foot of Ritigala, N. Central Province, Ceylon.
Biology.—The first specimen obtained was a statoblast fixed to a tube of the oligochæte wormAulophorus tonkinensistaken at Kawkareik in March. At the same time young zoaria, which did not yet possess a common investment, were found on a leaf growing on a twig which drooped into the water. Large compound colonies were taken in Orissa in October. They completely encased the stems of reeds, thus forming hollow cylinders, but slipped from their supports when the reeds were pulled out of the water. In life they resembled gelatinous algæ rather than animals and exhibited a striking similarity to masses of zoaria ofLophopodella carterisurrounded by such algæ. Some of the colonies were evidently dying and contained few polypides in a living condition, but many statoblasts; others were in a flourishing condition and were producing larvæ and statoblasts simultaneously.
A piece of a colony full of larvæ was placed before midday in an aquarium, which was kept in a shady verandah. Large numbers of larvæ were set free almost immediately. They measured about 2 mm. in length and were distinctly pear-shaped; each contained a pair of polypides, which occupied a comparatively small part of the interior, the whole of the broader half being hollow. The larvæ swam slowly, broad-end-first, by means of the cilia with which their surface was covered, occasionally gyrating on their long axis and always adopting an erratic course. Towards evening they showed signs of settling down, frequently touching the glass of the aquarium with their broad ends and sometimes remaining still in this position for some minutes. Many attempts were, however, made before fixation was completed, and this did not occur until after nightfall. By next morning every larva was fixed to the glass and had everted its two polypides. Unfortunately I was not able to trace the development further, but young compound colonies were found in which the secretion of the common investment had just commenced. The zoaria in these colonies measured about 1 cm. in diameter and already contained many polypides each.
Oka has described the development from the statoblast of the allied Japanese species. He found that each statoblast produced in the first instance a single polypide, and that the statoblasts, which were produced in autumn, lay dormant through the winter and germinated in spring. As the Sur Lake begins to undergo desiccation as soon as the "rains" cease, the statoblasts in it probably do not germinate until the break of the next "rains" about the middle of June. I have had dried statoblasts in my possession for over two years. Their cellular contents appear to be in good condition, although the cells show no signs of development; but they have not germinated in my aquarium, in which some of them have now been kept for more than six months.
The green cells of the common investment are peculiar bodies that deserve further study than it has yet been possible to devote to them. Each cell is of ovoid form, varying somewhat in size but as a rule measuring about 0.03 × 0.008 mm. There can be no doubt that these bodies represent a stage in the life-history of an alga[BO]. Diatoms, bacilli and other minute plants are often present in the membrane as well as the characteristic green cells, but do not form a constant feature of it.
[BC]Proc. Linn. Soc. N. S. Wales, xxxiv, p. 489 (1909).
[BD]Rousselet, Proc. Zool. Soc. London, 1907 (1), p. 254.
[BE]See Rec. Ind. Mus. v, p. 40, footnote (1910).
[BF]In specimens preserved in spirit they are apt to collapse and therefore to become somewhat concave.
[BG]Annandale, J. As. Soc. Bengal (n. s.) ii, p. 188, pl. i (1906).
[BH]See Michaelsen, Mem. Ind. Mus. i, pp. 131-135 (1908).
[BI]Braem (op. cit., p. 3, pl. i, fig. 1), has described and figured under the nameP. fungosavar.coralloides, Allman, a dense form that somewhat resembles this phase ofP. fruticosabut has become compacted without external pressure. It is, however, probably a form ofP. repensrather thanP. fungosaand differs in its broad statoblasts from any form ofP. fruticosa. I have examined specimens of the same form from England.
[BJ]But see p. 246 (addenda).
[BK]Only two species are known,L. crystallinus(Pallas) from Europe and N. America, with oval statoblasts that are produced and pointed at the two ends, andL. jheringi, Meissner from Brazil, with irregularly polygonal or nearly circular statoblasts.
[BL]Zool. Anz. xxxi, p. 716 (1907), and Annot. Zool. Japon. vi, p. 117 (1907).
[BM]Prof. W. West will shortly describe this alga, which represents a new species, in the Journ. Asiat. Soc. Bengal, under the nameTolypothrix lophopodellophila.—April 1911.
[BN]It is now perhaps open to doubt whether the investment is actually secreted by the polyzoon, for Prof. W. West has discovered in it the cells of an alga belonging to a genus which habitually secretes a gelatinous investment of its own (see p. 238,post.).—April 1911.
[BO]Professor W. West identifies this algæ asDactylococcopsispectinatellophila, new species. It will be described, before the publication of this book, in the Journ. As. Soc. Bengal (1911). Prof. West has found, associated more or less fortuitously withP. burmanica, another alga, namelyMicrocystis orissica, also a new species.—April 1911.
Hints on the Preparation of Specimens.
To preserve Spongillidæ.—Spongillidæ must be preserved dry or in very strong alcohol. Formalin should not be used.
To clean siliceous sponge spicules.—Place small fragments of the dried sponge (if alcohol is present, the reaction is apt to be violent) in a test tube, cover them with strong nitric acid and boil over the flame of a Bunsen burner or small spirit lamp until the solid particles disappear. Add a large quantity of water to the acid and filter through pure cellulose filter-paper, agitating the liquid repeatedly. Pass clean water in considerable quantities through the filter-paper and dry the latter carefully; place it in a spirally coiled wire and ignite with a match, holding the wire in such a way that the spicules released by the burning of the paper fall into a suitable receptacle. They may then be picked up with a camel's-hair brush and mounted in Canada balsam.
To examine the skeleton of a Spongillid.—Cut thin hand-sections with a sharp scalpel, dehydrate if necessary, and mount in Canada balsam.
To prepare gemmules for examination.—Place the gemmules dry in a watch-glass with a few drops of strong nitric acid. When gas is given off freely add water in considerable quantities. Remove the gemmules with a camel's-hair brush to clean water, then to 50%, 70%, 90% and absolute alcohol in succession, leaving them for an hour in each strength of spirit. Clear with oil of cloves and mount in Canada balsam.
To ascertain the presence of bubble-cells in the parenchyma of a Spongillid.—Tease up a small piece of the sponge with a pair of needles, mount under a thin cover-slip in strong spirit, and examine under a high power of the microscope.
To preserve Hydra in an expanded condition.—Place the polyp in a watch-glass of clean water and wait until its tentacles are expanded. Heat a few drops of commercial formaldehyde and squirt the liquid while still hot at theHydra, which will be killedinstantaneously. Remove it to a solution of formaldehyde and spirit of the following formula:—
Then pass theHydrathrough 50% and 70% alcohol and keep in 90%.
To examine the capsules of the nettle-cells.—Place a livingHydrain a small drop of water on a slide and press a thin cover-slip down upon it.
To preserve freshwater polyzoa in an expanded condition.—Place the polyzoa in a glass tube full of clean water and allow them to expand their tentacles. Drop on them gradually when they are fully expanded a 2% aqueous solution of cocaine, two or three drops at a time, until movement ceases in the tentacles. Then pour commercial formaldehyde into the tube in considerable quantities. Allow the whole to stand for half an hour. If it is proposed to stain the specimens for anatomical investigation, they should then be removed through 50% and 70% to 90% alcohol. If, on the other hand, it is desired to keep them in a life-like condition they may be kept permanently in a solution of one part of commercial formaldehyde in four parts of water. Care must be taken that the process of paralyzing the polypides is not unduly prolonged, and it is always as well to preserve duplicate specimens in spirit or formalin with the lophophore retracted.
To prepare statoblasts for examination.—Place the statoblasts for a few minutes in strong nitric acid. Then remove the acid with water, pass through alcohol, clear with oil of cloves, and mount in a small quantity of Canada balsam under a cover-slip, taking care that the statoblasts lie parallel to the latter.
The following addenda are due mainly to an expedition to the lakes of Kumaon in the W. Himalayas undertaken by Mr. S. W. Kemp in May, 1911.
PART I.
GenusSPONGILLA.
SubgenusEUSPONGILLA(p.69).
1 a.Spongilla lacustris, subsp.reticulata(p.71).
Specimens were taken in the lake Malwa Tal (alt. 3600 feet) in Kumaon, while others have recently been obtained from the Kalichedu irrigation-tank in the Pagnortalugof the Nellore district, Madras (G. H. Tipper).
4.Spongilla cinerea(p.79).
Specimens were taken in Naukuchia Tal (alt. 4200 feet) in Kumaon. They have a pale yellow colour when dry. This sponge has not hitherto been found outside the Bombay Presidency.
SubgenusEUNAPIUS(p.86).
8.Spongilla carteri(p.87).
Specimens were taken in Bhim Tal (alt. 4450 feet) and Sat Tal (alt. 4500 feet). Some of them approach the varietycavain structure.
SubgenusSTRATOSPONGILLA(p.100).
12.Spongilla bombayensis(p.102).
Add a new variety:—
13 a. Var.pneumatica, nov.
This variety differs from the typical form in the following characters:—
(i.) The sponge forms a flat layer of a pale brownish colour as a rule with short and very delicate vertical branches.In one specimen it takes the form of an elegant cup attached, only at the base, to a slender twig.
(ii.) The gemmules are covered, outside the spicules, by a thick pneumatic coat of irregular formation and with comparatively large air-spaces.
(iii.) The gemmule-spicules are regularly sausage-shaped.
Typesin the Indian Museum.
Habitat.Naukuchia Tal (alt. 4200 feet), Kumaon, W. Himalayas (S. W. Kemp).
GenusEPHYDATIA(p.108).
AfterEphydatia meyeni, p. 108, add:—
Ephydatia fluviatilis,auct.