The caudal vertebræ, on the contrary, are lessened throughout the Birds, to a degree met with in no other class of animals.
3389. The brain separates for the first time completely into cerebrum and cerebellum, begins to exhibit convolutions, and has in general most of the individual parts analogous to those in the Thricozoa. They are thereforeEncephalic animals, which the name of Neurozoa will properly enough imply. The nerves are in comparison with the spinal cord much thinner than in Reptiles and Fishes.
In the Bird also, all the spiritual or mental faculties make their appearance for the first time and suddenly, whereas in the preceding classes but slight traces of them were observed. Such for example are their mechanical instincts, varied modes of nidification, powers of imitation, susceptibility to instruction, knowledge of their benefactors, sentiment of joy, wheedling or coaxing manners, and so on. We have no example of Fishes and Reptiles having learnt any artificial tricks.
3390. Birds are the closest repetition of the Insects, but stand remote from the Crabs and Acalephæ, indications of which are reflected by their structure, disposition, mechanical instincts, and in their nests.
Thorax.
As the sexual body with the tail predominates in Fishes, and the abdomen in Reptiles, so does the thorax in Birds. The whole abdomen and sexual body has been subordinated to the thorax.
The ribs are here directed in such a manner for the first time, that the thorax can act as a voluntary pump-organ. Sternum and respiratory muscles are usually large and peculiarly built.
3391. The lung is only a cluster of Insect tracheæ. They are full of foramina, out of which the air can penetrate into the whole body, exactly as in Insects. In Fishes the lung was still an actual intestine, as seen in the single air-bladder; in Reptiles it was nothing more than a double intestine; in Birds this lung is divided after the fashion of an Insect into aerial vessels or ducts.
In the Bird the intestine lies in the air, and breathes from it, as in the Insect. Birds are also animals which breathe by the intestine.
3392. The whole Bird is lung. Its body is a thoracic cavity, while in the Fish it was simply a sexual cavity, and in the Reptile had obtained the abdominal form. In Birds therefore there is a number of ribs and a strong ossification, from the air itself penetrating into the bones.
Even the intestine has passed over into a motor organ. In Birds and Insects only do we find a true muscular stomach, wherein the food is crushed.
Members or Limbs.
3393. In these animals the formation of limbs or members must be wholly attained. Everything, that works, must work to the production of limbs. The whole body becomes limb.
3394. With the perfected nervous and respiratorysystem the bones and muscles make also a perfect appearance. The skeleton is hard, complete, and full of air instead of marrow; the muscles are red and separated, the movements free and complex.
3395. The elevated condition of the motor system is demonstrated in the limbs, which here appear in the greatest diversity. There are only two pairs of limbs, thoracic, and abdominal or sexual members. These two are equivalent, so long only as the sexual and abdominal cavity belonging to the trunk proper predominate, and therefore preserve the equilibrium. But the limbs, which have been given to serve the office of the trunk, are destined for progression or swimming, and are simply terrestrial or aquatic members.
3396. The higher limbs are thoracic respiratory members, which are filled with air and clothed with tracheæ, thus exercising a function conformable to the thorax. The thorax has an aerial character. The highest thoracic limbs must be aerial members.
3397. As the abdominal members move upon the earth or in the water, so do the thoracic in the air. The terrestrial limbs are feet, the aerial limbs,wings.
3398. The wings are in the member-formation the extremes of the thoracic limbs. It does not follow from this that they are the noblest in rank, but only that they are the uttermost unto which bodily motion can attain.
3399. The winged animal is the Bird.
3400. The Bird is an Insect with fleshy limbs.
3401. The wings of Birds repeat the alary appendages of Insects in the flesh.
3402. A Bird's wing is a strange but very instructive composition. It consists, namely, of a Reptile's foot and an Insect's wings.
3403. We saw how the branchiæ of the Insect dried up, separated from the feet, and being liberated as wings, were permeated by tracheæ. In the Bird these wings have remained standing upon the feet and been converted into feathers.
3404. A feather is an Insect's wing.
3405. As the Bird grows out at the thoracic limbs into the Insect's wings, so does it upon the whole body into dried branchial laminæ.
The whole body of the Bird is clothed with branchial laminæ or plates.
3406. The wings of the Insects might be called free tracheæ.
The Bird's feathers are Insect-tracheæ. As in the Insect the wings are a leash or net of tracheæ held together by membranes, so feathers are tracheæ dividing into fibre-like ramules.
3407. The Bird is a Reptilian or Frog's body, beset all over with Insects, like as with parasitic animals.
3408. The highest Insect only attains to the possession of four wings, which in some Moths split again into several feathers. In the Bird a vast number of such wings originates.
3409. An Insect's wing is not more thanonefeather, and is therefore placed also directly upon the body. These wings must multiply so soon as they occur upon a membered trunk, upon arms. Thus, we need not ask why the Butterfly has four, but the Bird only two wings, seeing that the latter is the nobler animal. The discourse cannot be concerning the wings of the former, for the Butterfly has indeed none, but only four feathers.
3410. What the Bird is, it is by virtue of its feathers. It is throughout a trachea, a pair of bellows. Its bones are hollow, full of air, and stand likewise in communication with the lungs; the feather-quills are also hollow.
Senses.
3411. The wings have all the muscles to themselves; the bone has in them gone to ruin. On the legs, on the contrary, the muscles have declined, and the bone has got the upper hand.
Hence it results, properly speaking, that only the thoracic members are perfected, because the Bird is nothing but thorax. The abdomen has, so to speak, vanished,and through this the abdominal limbs are left only, as thin and dry poles or staffs.
3412. From the same cause the muscular flesh upon the head has disappeared. Neck and head are lean, or like Insect horn, which serves only the nervous system.
3413. Beyond the excess of motion the sense of feeling has been nearly lost. The toes are simply destined for motion, and to be used as scrapers, and the digits have become the supports of feathers.
3414. The bill is an Insect's proboscis. In the Bird no teeth whatever project from the flesh, but the jaws themselves. To such an extent has the flesh been withdrawn. What has been called the cere is the only remnant of the facial flesh. Even nostrils and tongue have suffered ossification.
3415. The tongue is a feather. Saliva is scarcely present.
3416. The ears, as being the sense of motion, are far more perfectly evolved than in all the preceding classes. They have opened outwards, and possess an additional auditory part, the cochlea.
With the limbs the sense of hearing must of necessity grow perfect.
3417. The Bird is thoroughly, or "out-and-out" organized as an animal of song. In it Nature attains unto a definite hearing and speech. The Bird speaketh the language of Nature.
With the Bird, the voice, properly speaking, breaks forth for the first time, and that too in a high grade of perfection, as melody.
3418. The ear is the highest representation of the trachea in muscles and bones. The Bird is theOtozoon.
Sexual Parts.
3419. The kidneys are symmetrically constructed, although not yet a perfectly coherent mass. They are of very large size. But a strange feature has come to pass in the urinary cyst, which is the sexual lung. Into this, as has been already said, the intestine opens, andthus it here again passes over into the lung, just as it has passed over into a fleshy cardioid stomach, and completely upwards into the feather-like tongue.
Into this sexual lung the seminal ducts also enter, or the penis, when one is present, along with the oviduct.
3420. The ovum consists of two completely separated substances, and these indeed are so distinct, that the vitellus is secreted at an entirely different place to the albumen, the former in the ovarium, the latter in the oviduct—whereas in Fishes both originated together.
The separation cannot extend further, or else the substances would no longer unite with each other, and the vitellus must be first mixed with the albumen, after it has been completely formed, after or when it is an embryo. In the Bird albumen and vitellus come together during their passage out of the parent's body, or in the act of being laid, and thus before the albumen has been converted into the chick. But in the Mammalia they are first completely united, subsequently to their being laid—i. e. during the period of lactation.
3421. The vitellus is directly secreted from the arteries, but the albumen from an enteroidal sac or the oviduct, which is finally converted into mammary glands.
3422. The vitellus is more a product of the thorax, and is therefore formed directly into the intestine and entire embryo.
3423. The albumen is an intestinal or digestive product, a solution of the organic mass into protoplasma or primary mucus. It is not fashioned itself into the embryo, but is only absorbed as fluid nutriment by the latter.
3424. The shell of the ovum is the last bone, which the animal deposits from the sexual blood, as being analogous to the urine. It is an aerial product, or an analogue of the feather's quill.
3425. Even the nest of the Bird is a spiritual repetition of its plumage, for in it the stalks of plants, tracheæ, or feathers are united into one body, which reminds us in the Swallows of the Acalephæ.
FIFTH CIRCLE. AISTHESEOZOA.
Class13.Aistheseozoa.
3426. An animal with all its organs of sense perfectly developed, is aThricozoon.
3427. The nervous system emerges at length freely above the other systems, and it is no longer its mass, but itsorganswhich impart character to the animal. The nervous organs are, however, simply the organs of sense. Through these therefore must the present differ from the preceding class of animals.
3428. Now too the senses first make their appearance in a self-substantial manner above the other organs, serving merely their own functions, and only by chance those of others.
3429. As in Birds the whole body was subordinated to the thorax, in Reptiles to the abdomen, in Fishes to the sex, in Insects to the tracheæ, and so on; in like manner is it here subordinated to the system of the senses or the head.
3430. As the higher senses determine or define the anterior part of the head, and are in their state of perfection provided with muscles; so here the face or visage is invested by flesh, whereby, properly speaking, a true, namely, a moveable countenance, first originates. The Aistheseozoa have afleshy face.
3431. All possess moveable eyes; fleshy noses, which stand open both externally and internally; ears opening outwards, and mostly provided with a moveable flap; a fleshy tongue, free in front, and moveable lips; with at least thoracic limbs and a skin covered with hairs.
3432. In the Bird, Reptile, and Fish the face is merely invested by tegument, nearly devoid of any muscles, and therefore immoveable. They have ategumental face, which is incapable of producing any expressions.
3433. In the tegumental face the eyes are motionless, and very rarely both directed so forwards that they canview an object together; the nostrils are frequently devoid of a fleshy rim; the tongue often feather-like, cartilaginous, or covered with teeth; true fleshy lips are wanting, as are frequently the teeth, with even the limbs and digits, or these are divided into a number of rays, forming either feathers, or fins; in the Aistheseozoa there are never more than five toes present, and if there be fewer, then the number admits of being referred to some crippling of the normal quantity, five.
3434. It is remarkable, and serves to the discovery of many laws, that the highest sense here appears for the first time in its state of perfection. The eye in the Aistheseozoa is present in a perfect condition throughout the class, with the exception of the eyelids; the other organs of sense are, on the contrary, exhibited in all their gradations of structure.
3435. It appears, as if the whole animal was first perfected, when the eye is present with all its investment or clothing. The eye of the Aistheseozoa has not simply all its internal chambers and all its humours, but also all its muscles; it is moveable and has perfect eyelids, with very few exceptions—Ophthalmozoa.
3436. The ear now begins to suffer arrest. Its completion is indeed the formation of an external concha or flap for receiving the rays of sound, the hand being repeated in the ear, and its skeleton constituted by the auditory ossicles. This auditory hand occurs only in the Aistheseozoa, and might serve as characteristic if it were not wanting in many, while the eyelids are present. As in the Whales, where the auditory passage can be, however, closed, an act which is not possible in any Bird. The Bird must hear whether it will or no.
In all Thricozoa the interior of the ear is perfect, having cochlea, semicircular canals, tympanum, and, as brachial parts, the three conjoined auditory ossicles. The concha of the ear passes besides through all stages of development, from having a simple margin to one with most varied convolutions, lobes and opercula.
3437. Still more than the ear does the nose undergomodifications. In the Whales it seems to be less adapted for the purposes of smell than of respiration. The olfactory nerves are in them very delicate, and the apex of the nose is destitute of motion.
In other beasts, on the contrary, it is elongated into a very muscular proboscis or snout, and is endowed with the power of voluntary motion.
The form also of the nostrils is very varied, they being round, narrow, patulous, and frequently capable of being closed.
3438. The tongue is indeed mostly fleshy and soft; yet in many species it is provided with horny points, in others invested by a dense coriaceous tegument, so that it appears to represent an instrument for deglutition rather than gustation.
3439. The lips also are mostly fleshy and moveable; yet in many they retrograde exceedingly and lose their mobility, as is partly the case in the Ornithorynchus.
3440. In most, however, the limbs, especially the toes, are still subject to variation. Their perfection consists in the number five, and in the difference between the two pairs of limbs, as in Man. In the Apes the posterior feet are also hands, which is an imperfection; in the Marsupials there are hands posteriorly but toes in front; in other respects there are generally toes, sometimes five, then four, finally two perfect and two dew-claws in the Ox, and at length only one in the Horse, while the posterior extremities are virtually lost in the Whales.
3441. The dental system, as being the set of maxillary claws, is alone present in its state of perfection in the Thricozoa. They alone have, in addition to the incisor teeth, all the five kinds of teeth that differ from each other in form, namely, canine, false molars, laniary, with second and third true molars, corresponding to the five fingers reckoned from the thumb.
3442. In the dentition of those animals which tear their food the greatest amount of completeness and variety is met with, since each tooth has a different form and function.
In the Bears the molars are uniform in character, and so on through the Apes up to Man.
In the Marsupials they are tolerably similar, as also in the Bats and Shrew-mice.
They are still more alike in the Pig and Horse, and the incisor teeth begin to be wanting in the Ruminantia, e. g. the Ox.
In Mice the canines are wanting, in the Sloths the front teeth, and in the Ant-eaters actually all.
3443. In opposition to the perfect eye the general sense of feeling is developed in the tegument. The tegument which is best developed will be that, which represents a self-substantial organ with all its appurtenances, and thus an organ of touch, whose nobility of rank consists in motion. A skin, which is moveable by means of muscles, must take the noblest rank. A skin withtegumentalmuscles is an organ of feeling, which is already in some degree subjected to the influence of the will. If tegumental muscles do not occur in all these animals, they still do in most of them.
The production of the most perfect coat or covering is the second step, whereby the tegument ascends.
3444. Hitherto the outer covering of animals was pretty inorganic, consisting either of hollow tracheæ, feathers, or semicavernous scales, coat of mail, or lastly, only mucus. All these organs were only constructed after the type of individual vegetable systems, in greatest part only after the respiratory organ, and were therefore partial in aspect or deficient.
The highest covering must also bear the highest meaning. This is that, which grows out of the sanguinary system collectively, out of the capillary vessels. The capillary vessels of the covering are, however, the hairs. The hair is the most perfect covering of the animal.
3445. These animals are theThricozoa.
Already the highest birds, e. g. the Ostrich and Cassowary, exhibit feathers which merge over into hairs.
3446. An integument clothed with hair, and self-substantially moveable is the perfection of this organ, it is afur—Furred animals.
3447. The fur is the peripheric combination of the Vegetable and Animal. The hairs are the highest Vegetable, as being the vascular system grown out of or above the animal, and constituting the fundamental or basi-system of the whole body. The tegumental muscles are the lowest Animal. In the fur consequently the whole animal has been represented, but as a limit set between animal and world.
3448. The tegumental covering also varies. The hairs become scanty in respect of number; instead of them spines, horny rings or scales occur, yet there are always hairs on the belly. In many Whales they seem to dwindle into bristles. In some they have coalesced to form a kind of bark, as in the Stellerian Walrus or Sea-cow.
Thorax.
3449. In all the respiration is aerial; in all there is a true costal structure, and a respiration effected through the motion of the ribs or a pumping action; in all the lungs are filled with cells; in all there is a diaphragm, a larynx, a trachea with cartilaginous rings, and a thyroid gland. But the air no longer penetrates from out the lungs into all the cavities of the body, as in Birds.
Abdomen.
3450. The two intestines, namely, the large and small, are more distinct from each other than in other animals; the cæcum coli is in most distinct; the stomach expanded and membranous in texture, so that it operates simply through chemical influence. Liver, pancreas, and spleen occur in all.
3451. The sexual parts are in every respect very perfect. The penis is present in all, and all have an uterus, fallopian tubes, and separate oviducts. The penis is inmany still retracted into a cloaca, and the testes frequently lie within the abdominal cavity.
3452. As in the tegument the parts separate and each becomes self-substantial, the fibre animal, the tegument vegetal, and so on even in the sexual animal. The ovarium, consisting of two parts, now also separates, since one becomesanimal, but the other remains vegetal. The albumen-organ becomes animal, detaches itself from the sexual parts, is developed in the self-substantial tegument and called mamma.
The Aistheseozoa are thus alsoMastozoaor Mammalia.
3453. This separation of the sexual animal is one of the first characters. The mammæ could never be wanting, because they indicate an essential stage in the development. The albumen-organ becomes an organ of sensation. If the existence of mammary organs be doubtful, as in the Ornithorynchus, the hairs are in that case perfectly distinct. No Reptile nor Bird can have hairs, because their covering is derived only from a partial system, the respiratory; while hairs are from the general vascular system, which is the foundation of the tegument, of the sense of feeling. The Ornithorynchus is afurred animal, and this would suffice to bring it among the Aistheseozoa, were we even to deny it mammary organs.
3454. Both sexes, male and female, have breasts. In youth they are most readily detected in the male, because their sexual parts then rank nearer to the female. In other respects the mammæ are probably the chiefest organs of absorption for the embryo.
3455. The mammæ are nobler in rank, when, as udders they become self-substantial; and the more they remove from the belly or abdomen, and come, as breasts, to be placed upon the chest.
3456. Had the names been given in strict accordance with rank; then the class-divisions, which correspond to the circles, would have been calledOrders.
3457. Families would be class-divisions, which correspond to the classes themselves.
3458. In no class therefore could there be more than four orders admitted, or five, if the sensorial organs be reckoned to constitute a special circle.
From the same reason there are no more than thirteen or seventeen families.—These names cannot meanwhile be so strictly adopted, because the classes are not of equal rank, as has been observed; on this account it is necessary to shove in here and there other divisions, which should be termed at one timeCohorts, at another,Alliances.
3459. If the animals of a class differ from each other, it is only possible by their bringing to bear in addition to their characteristic organ some other organ, and consequently becoming similar to an earlier or later class.
3460. Yet nevertheless in this ascent the animals could never outstep the confines of their own circle. There can be no Dermatozoon which could have bones; for in that case it would be an Osteozoon, and belong to another province.
Every class therefore comprises as many orders only as there are circles with which it comes into contact. Thus in the first circle there is only one order, in the second two, and so on.
Each class therefore includes also as many families only as the circles which are touched by it contain classes. Thus the first to the third class has three, the fourth to the sixth, six; the seventh to the ninth, nine; the tenth and so on, thirteen.
3461. The serial arrangement of animals into families is naturally difficult; but in Physio-philosophy we have to treat not about the execution of the Systematic in detail, but concerning its principles.
FIRST CIRCLE. INTESTINAL, OOZOA—MUCUS-ANIMALS.
First Class.
Gastric, Vitelline Animals—Infusoria.
3462. The Infusoria admit of being reduced to three divisions: the lowest of which, such as the Infusoria proper or Monades, are provided for the most part with cilia; the next in succession, as the Rhizopoda, possess extensible processes, and are mostly covered by a multi-chambered shell; lastly, the most perfect Infusoria have all kinds of internal organs, and especially what has been called rotatory apparatus, as being the dawn of future tentacula.
3463. These three Families obviously correspond to the three classes of the present circle, and that indeed as follows:
To thefirst class, or Infusoria proper, correspond theMonades.
To thesecond class, or Polyps, theRhizopoda.
To thethird class, or Acalephæ, theRotifera.
3464. The Monades are obviously the simplest organized creatures, being mucous vesicles, which move, obtain their food by stirring up vortical currents in the water, and emit what is undigested again by the mouth.
3465. They occur very abundantly in all infusions, and can very well originate, like Fungi, by division of the organic mass, although they are in a condition to propagate themselves, i. e. by spontaneous division.
3466. The Monades are the semen of the animal kingdom, which is dissolved in, or rather produced from, the sea.
3467. The animal body is nothing else than a compound fabric of Monads.
3468. Decomposition is a separation into Monads, a retrogression into the primary mass of the animal kingdom.
3469. All propagation, even that of the sex, commences like the animal kingdom, or with its first family. On that account the embryonic development must be a passage through the animal kingdom.
3470. The Rhizopoda usually adhere together within amulti-chambered calcareous shell, out of which they protrude mucous filaments, and are therefore the antetypes of the Corals or Polyps.
3471. The Rotifera exhibit all kinds of viscera, such as intestine and ovaries; besides what have been called rotatory organs, which remind us of the arms or tentacles of the Acalephæ.
3472. The families of these animals may be therefore aptly named as follows:
Fam. 1. Typical Infusoria—Monades; cilia or vibratile organs.2. Polypary Infusoria—Rhizopoda; extensible processes.3. Acalephan Infusoria—Rotifera; intestine and oral organs.
Second Class.
Intestinal, Albuminous Animals—Polypi.
3473. The Polyps also do not admit of being divided into more than three families. The first are only tubes or vesicles withcapillary tentaculaaround the mouth, as the naked Polyps, Tubulariæ, Sertulariæ, and Cellulariæ.
The others have true ciliatedtentacular rayssurrounding the mouth, and are always condensed inferiorly into a horny, and occasionally stony axis or stem, as is seen in the Gorgoniæ, Alcyoniæ, and Isidiæ.
The third have ordinarytentacula, occurring in great numbers like tassels or tufts around the mouth; their integument is either hardened into stone, or becomes fleshy, as in the Star-corals and Actiniæ.
3474. There is no doubt that thenaked Polypsare closely allied to the Infusoria, and among them indeed to the Rotifera, so that they represent but a higher stage of these creatures, characterized by superior size and by tentacular in place of ciliary or vibratile hairs.
3475. TheCellulariæcannot be more distinctly characterized than by saying that they are cortices or ramules inhabited by Vorticellæ. Thus they are Vorticellæ surrounded by a shell, and may be compared to ova, in whose coriaceous or leathery shell calcareous granules are blended, as in the eggs of the Crocodiles and Tortoises.
3476. They increase by means of ova and by ramification, if the former mode of division is not carried too far.
3477. The tubes of the Tubulariæ appear to be nothing else than the posterior extremity of the Polyp, desiccated or dried. These tubes are not therefore the product of an excretion, but the body itself.
3478. On the contrary, the tubes of the Sertulariæ must be held as being a tegumental excretion, within which the Polyp ramifies and produces ova-cysts. If the naked Polyps resemble ova which are devoid of shells, such as the roe or spawn of Fishes, then the Sertulariæ resemble ova surrounded by a tough skin, like those of Rays and Serpents.
TheRadiated Polypsor Horn-corals are invariably ramified and converted towards their interior into a common horny or stony mass; so that the animals themselves appear to have coalesced upon this into a common tegument or bark. They possess a stomach and ovaries surrounding it, which open into the border of the mouth between the rays. They thus increase by ova and ramifications.
They therefore represent the class proper of the Polyps.
The tufted Polyps comprise the proper Corals or Lithozoa, are in form and substance like the Acalephæ but with this difference, that the covering is mostly lithoidal, while in many Acalephans, as the Porpitæ, it only appears as a cartilaginous disc or plate.
3479. These Corals are true ova, having a perfect calcareous shell, like that of the Bird. The gelatinous animal which adheres within a wide-mouthed Madrepore, e. g. Fungia, resembles a vitellus just hatched, and from which the fœtal envelopes have been developed.
3480. The numerous tentacular filaments surrounding the wide mouth resemble the shags of the chorion, which accumulate around the orifice of the umbilical cord to constitute a placenta in the higher animals.
The Corals are brood-eggs inclosed within the uterus of Nature or in the sea. The Coral-animals are an umbilical cord, treasured up for the embryo, while the Tubulariæ are only membranous vitelli, and the Gorgoniæ, ova with desiccated albumen.
3481. The families of Polyps stand therefore in the following order of significance:
Fam. 1. Infusorial Polyps—Tubulariæ.2. Typical Polyps—Alcyoniæ.3. Acalephan Polyps—Actiniæ.
Third Class.
Absorbent, Involucral Animals—Acalephæ.
3482. The Acalephæ also can only be brought under three divisions, viz. Röhrenquallen, orPhysaliæ, Rippenquallen orBeroes, Hutquallen orAcalephæ.
3483. ThePhysaliæare without doubt the lowest, being only giant Infusoria; theBeroesare allied through their simple bodily cavity, to the Gorgoniæ; theAcalephæ, through their form, to the Madrepores, especially the Actiniæ.
3484. They range therefore in the following order of significance:
Fam. 1. Infusorial Acalephæ—Physaliæ.2. Polypary Acalephæ—Beroes.3. Typical Acalephæ—Acalephæ.
3485. Thefirsthave not yet attained to the unity or single character of the mouth, but imbibe their food through numerous tubes. They are bundles of ramified Vorticellæ, a thoracic duct full of glands and roots, which absorbs nutriment out of the sea, instead of an intestine.
As the first family they are the antetypes of the Mussels and Entozoa, and especially of the Hydatids and Tape-worms, and we shall not be far from hitting the mark, if we compare their air-bladder with the hindermost cystiform member of the body in the Hydatids.
3486. Thesecondfamily have a single mouth and ribs mostly full of lamellæ, which are probably the antetypes of gills; they are also frequently traversed by nutritive vessels.
They are antetypical of Snails, being in form an abdominal pouch, in substance a liver, and frequently possessing paired tentacula. Higher up, and they indicate the Crabs.
3487. Thethirdhave, as a general rule, one centralmouth surrounded by four arms and very numerous vessels, which run from the gastric cavity to its margins, and there mostly elongate into filaments or hairs, being thus true lymphatic vessels, which convey the nourishment directly from the stomach through the whole body, and become on its margin tentacula.
3488. As antetypes of the Kracken they particularly manifest the form of the Sepiæ, or Cephalopods, in the strong and frequently papillated arms that surround the mouth. Gland-like nodes are also developed in the margin of the pileus, but their meaning is as yet doubtful. Upon a higher stage, and they are antetypical of Insects.
Their vascular system forms an exceedingly regular, quaternary net, with branches and ramules ranging opposite to each other, which have been believed to be the vitelline network of the ovum when hatched. These vessels terminate likewise in a common marginal vessel, as in the vitellus.
3489. Viewed as a whole they resemble in form, appendages, and substance the fœtal involucra or envelopes. The upper surface may be compared with the convex back of the envelopes, the lower to the concave funnel of the umbilical cord, and the succigerent filaments or hairs to the shags of the chorion. They are probably elongated by injection, like the so-called legs of the Star-fishes.
The secretion of the ova in four ovaries speaks also in favour of their higher grade of development. They lie in four cavities around the stomach, which also open near to the mouth. Their size also is significantly expressive of their higher position.
Finally, they are of separate sexes. In them is the milt for the first time distinctly displayed, and in the same situation indeed where in other animals the ovaries are.
3490. Hence, in these three classes there are found no more than three families, which together make up onlyoneorder. The want of a fourth family and so on, proves that the development of these animals does notpass over into the succeeding circle. Their body therefore is only an homogeneous, transparent mass, variously excavated and perforated, but not separated into two cysts, namely, tegument and intestine, and without the other viscera, which are formed by the vascular system, such as the liver, kidneys, and salivary glands.
SECOND CIRCLE. VASCULAR, SEXUAL ANIMALS.
3491. These animals will both traverse the three classes of their circle, as also repeat the preceding three classes, and they consequently divide into two orders and six families.
Fourth Class.
Venous, Ovarial Animals—Mussels.
3492. The Mussels or bivalve Mollusca resolve themselves into two orders, according to the structure of their mantle or respiratory sac. It is either closed in a tubuliform manner, and opens posteriorly into two mostly tubular-shaped respiratory apertures, and in front has an orifice for the passage of the foot—Camacea(Lochmuscheln); or it is slit along its whole length anteriorly; and the pedal aperture is confluent with the anterior and also indeed with the posterior respiratory opening—Ostracea(Spaltmuscheln.)
The first order still represent the cystic form of the Oozoa, and partly by tubuliform calcareous shells placed around the two ordinary shell-valves; but the second, by the freer development of the organs, represent the animals of their own circle.
Order1.Protozooid Mussels—Lochmuscheln.
3493. These animals repeat the Mucus-animals; are tubular in form, and mostly provided with two long respiratory tubes.
Fam. 1. Infusorial Mussels—Sackmuscheln or Pholades.
Cylindrical, with a tubuliform mantle almost entirely closed and frequently surrounded by a calcareous tube, in addition to the two ordinary shell-valves; the pedal aperture is situated at the oral extremity; the respiratorytubes retractile by means of muscles; the foot is cylindriform.
Of the same kind are the Pfahlmuscheln, Teredines, and Sandmuscheln, as also the Solenidæ. They typify the Nudibranchiate Snails and the Salpæ.
Fam. 2. Polypary Mussels—Klaffmuscheln or Tellinidæ.
Body flat, mostly discoidal; there is a large fissure on the abdominal side of the mantle for the passage of the foot, while posteriorly there are two long respiratory tubes with retractor muscles. Here belong the Tellinidæ and Venusidæ.
I have shown, that they are already to be recognized by the uncinate or hook-shaped groove for the mantle in the shell, and which proceeds from the insertion of the retractor muscles. The foot is usually lancet-shaped. They typify the Patellæ and Ascidiæ.
Fam. 3. Acalephan Mussels—Cardiacea.
Body globular in form, mantle having a pedal slit on the abdominal side; two respiratory apertures without retractor muscles; foot mostly uncinate or strap-shaped.
T have shown that these creatures are to be recognized by a discoid groove in the shell, which simply depends upon the mantle, the retractor muscles being wanting. Here belong the Cardiacea and gigantic Chamidæ, in which last a byssus occurs, and the union also of the two occlusor or sphincter muscles, as in the following order. They antetypify the air-breathing Snails and Cirripedia.
Order 2. Conchozooid Mussels—Spaltmuscheln.
3494. These animals represent their own circle.
The pedal slit in the mantle occupies the whole length of the latter, and is confluent with the anterior or also with the posterior respiratory aperture; so that only one or even no aperture is left, and this when present is besides never elongated in a tubular form; the retractor muscles are therefore wanting also, and the shell simply exhibits a discoid groove for the mantle. The occlusor muscles approximate and unite at their terminations. Both usually coalesce into one.
Fam. 4. Typical Mussels—Mytilaceæ.
Occlusor muscles separate, and mantle slit to such an extent, that only the posterior respiratory aperture remains; foot mostly tongue-shaped or coniform, with occasionally a byssus.
Here belong the fresh-water Mussels and the Mytili proper, of which last many bore into rocks. They typify the Capulidæ and Brachiopoda.
Fam. 5. Snail-Mussels—Arcaceæ.
Have two separate occlusor muscles and a perfectly separate mantle without respiratory aperture; the foot small, mostly cartilaginous. Here belong the Arcæ, Aviculæ, and Pearl-mussels.
They typify the Trochidæ and Pteropoda.
Fam. 6. Kracken-Mussels—Ostracea.
Onlyoneocclusor muscle, mantle entirely open or slit, so that both respiratory apertures are only oblique incisions therein; foot very small, frequently furnished with a byssus. They typify the Buccinidæ and Cuttle-fish.
Fifth Class.
Arteriose, Orchitic Animals—Snails.
3495. The Snails likewise divide into two orders, according to the two circles, preindicated by the Ovum-and Sexual system. Their branchiæ are either ramulate or pectiniform, the sexual parts combined or separated.
The first kind are still frequently gelatinous in texture, transparent and naked; their branchiæ usually stand out freely as filaments, lamellæ, or ramules upon the back, or lie simply as a vascular network within the mantle. All are androgynous. They therefore obviously repeat the Protozoa or Mucus-animals.
The second are invariably covered by the shell and by a mantle, within the cavity of which the branchiæ lie concealed as one or two comb-like bodies. Tentacula and eyes, which are occasionally wanting in the preceding order, are here universally present; the sexes separate.
As in the Snails, the male parts make their appearancefor the first time distinct and individualized, and are also a characteristic organ of the class; so also do they serve as bases of division, and the Snails may be divided into those which are Androgynous or bisexual, and those with separate sexes, i. e. Diœcious.
Order 1. Protozooid Snails—Androgyni.
3496. The male and female sexual parts united together in a single individual, branchiæ ramuliform, occurring either as filaments, leaflets or ramules, freely situate upon the naked body, or as a network lodged within the pallial cavity and surrounded by a shell.
The Nudibranchiate species live in the sea, those with hollow branchiæ or the Pulmonea in the air; the former feeding mostly upon animals, the latter upon plants.
Fam. 1. Infusorial Snails—Notobranchiata, or Tritoniæ.
Body gelatinous and membranous, cylindrical and naked, devoid of shell, with branchial filaments or ramules disposed in two rows upon the back.
Here belong the Tritoniæ and Dorides. Their body is muscular; the tentacula not retractile; the male sexual parts open in company with the female upon the right side of the neck, as in the higher organized Snails. All inhabit the sea. They prefigure or typify the Salpæ.
Fam. 2. Polypary Snails—Pleurobranchiata, or Patellæ.
Body and sexual parts as in the preceding family, the branchiæ, however, occurring as ramules or leaflets upon the sides of the body, are more or less covered.
Here belong the Phyllidiæ, Schüssel-and Schildschnecken. They are the antetypes of the Ascidiæ.
Fam. 3. Acalephan Snails—Dictyobranchiata or Limacidæ.
The branchiæ form a rete or network within the pallial cavity, and respire the moisture of air; mantle and viscera are mostly surrounded by a shell; the body is therefore bipartite, being separated into a splanchnic or visceral body and a foot with head.
Here belong the Air-breathing Snails, both land as well as fresh-water species. They typify the Cirripedia.
The shells are mostly thin and horny, yet nevertheless contain a considerable quantity of calcareous earth, and are mostly devoid of opercula.
Those species, which dwell in fresh water, do not possess introvertible tentacula like the marine Snails, and the eyes are placed at their basis; the sexual orifices are separate.
In the Land-snails, the tentacula are introvertible, and support the eyes upon their apex; the sexual apertures are blended into one. The former, like the marine Snails, lay numerous small ova inclosed within a gelatinous mass in the water; the latter deposit their ova free, covered with a membranous, and occasionally calcareous shell, in the earth. Copulation is effected in all by a reciprocal interchange of the androgynous species.
I have observed that individuals of Limnæa auricularia can continue to propagate for several generations without being impregnated; theymust impregnate themselves.
Order 2. Conchozooid Snails—Diœcii.
3497. Branchiæ situated within the cavity of the mantle, and hanging down in the form of a comb; shell for the most part spirally contorted; sexes separate—Pectinibranchiata.
Here belong the Capulidæ, Turbinidæ, Neritæ, Conidæ, Volutidæ, Buccinidæ, Muricidæ and Strombusidæ.
The tentacula are not retractile, and have the eyes mostly seated at their basis; the penis is external, very large, and cannot be drawn within the body, but is only reflected into the pallial cavity; most of them have a protrusile perforating proboscis, and an operculum. They lay numerous small ova, contained within large membranous cases, which frequently hang in rows to each other like a necklace of pearls. The shells are in some instances horny, in others of a stony texture.
Fam. 4. Mussel-Snails, Capulidæ.
Only one branchial comb within the mantle, and covered merely by a flat hood-shaped shell; no operculum.
Here belong the Capulidæ; all the species are marine. They prefigurate the Brachiopoda.
Fam. 5. Typical Snails, Turbinidæ.
Two branchial combs, mantle devoid of a respiratory groove, shell turbinated; mostly furnished with an operculum, and that indeed of a stony texture. Here belong the Turbinidæ, and Trochidæ, such as the Cyclostomata, Paludinæ, Ampullariæ, Janthinæ, Neritæ. Live in the sea and in fresh-water.
Fam. 6. Kracken-Snails, Buccinidæ.
Like the preceding family, but their mantle has a groove, and there is a horny operculum. Here belong the Conidæ and Volutidæ, Buccinidæ, Muricidæ, Strombusidæ. Almost all live in the sea and are of sanguisugal habits. They antetypify the Cuttle-fish.
Sixth Class.
Cardiac, Nephritic Animals—Kracken.
3498. Body cylindrical, without sole or foot; frequently venous hearts together with the arteriose hearts, and a kidney-like organ.
Such are the properCylindrical Snails, which are either sessile or fixed, or move themselves by fins and what have been called arms—Sessile and Natant Kracken. Here belong the Salpæ, Cirripedia, Brachiopoda, Pteropoda, Heteropoda, and Cephalopoda. They all live in the sea.
Branchiæ and sexual relations very varied.
They divide likewise into two orders, in accordance with the two circles of Mucus-animals and Conchozoa; the former are spathiform, mostly gelatinous, and firmly sessile or fixed; androgynous, without head and rudders or fins. The branchiæ trellis-like and filiform—Ascidiæ, Cirripedia and Brachiopoda.
The others have a kind of head with arms and eyes, or fin-shaped steerage-organs upon the body; branchiæ pectiniform, reticular, and leaf-shaped—Pteropoda, Heteropoda, and Cephalopoda.
Order 1. Protozooid Kracken—Rumpfkracken.
3499. Body sacciform, mostly gelatinous, without head and eyes; species androgynous. They are destitute of independent locomotion, most of them being quite stationary or fixed, and surrounded frequently by a shell; some few float about passively in the sea.
Fam. 1. Infusorial Kracken—Salpæ.
TheSalpæare gelatinous, freely natant cylinders, perforated by an open tube, within which are situated the branchiæ, heart, mouth, intestine, and liver, without any tentacula. They continue to hang for a long time to each other, as though they were in the ovary.
They undergo a remarkable metamorphosis, which traverses two generations, the young meanwhile not resembling the mother but the grandmother.
Body within a sacciform mantle, with two opposite respiratory apertures.
Fam. 2. Polypary Kracken—Ascidiæ.
TheAscidiæhave a sacciform body with two co-approximate respiratory apertures; branchiæ internal and trellis-shaped.
These gelatinous or cartilaginous animals adhere firmly to rocks, with the respiratory apertures directed upwards as in the Mussels, but the branchiæ are not foliiform; the internal cavity is lined with a membranous sac, upon which the branchial vessels are dispersed in a trellis-like manner. At the bottom of and within the sac is the mouth, which is destitute of tentacula. Intestine, liver, and a heart that is simple or undivided. Mode of propagation unknown.
They are frequently connato-sessile, like the Polyps.
Fam. 3. Acalephan Kracken—Cirripedia.
Body sacciform, without branchial openings, oral apertures situated at the inferior extremity of the longitudinal fissure in the mantle, and provided with a kind of maxillary apparatus; above or behind the mouth are annulate or horny filaments representing caudal fins or feet, upon the basal joints of which is a branchial filament. Here belong the Balani and Lepades—Fuss-kracken.
These animals are likewise sessile, at least when full grown, and are surrounded by shell-plates, which remind us of the Echini or Sea-Urchins, whose antetypes they are; this resemblance is particularly distinct in the Balani, which have similar odontoid valves upon the aperture or mouth of the shell. These animals also undergo a metamorphosis, since in the early periods of their existence they swim about like small Crustacea, and later on become fixed or sedentary, and surrounded by the plates of shell.
The Lepades have the ordinary shells of Mollusca, but each of the two valves consists of two pieces, between which an odd one is interposed down the back.
These five shell-pieces become in the Balani a regular set of teeth, which are adherent within the cylindrical shell, by which the posterior part of the body, or the peduncular and elongated mantle, is surrounded. (Vid. Oken's 'Allgemeine Naturgeschichte,' V, 1835, 509.)
They bear a resemblance to the Crustacea, not simply in the annulate horny feet, but also in the double and ganglionic nervous chord lying along the abdomen; only they are androgynous, which occurs in no Crustacean.
Order 2. Conchozooid Kracken—Kopfkracken.
Tentacula upon the head or fins upon the body. They repeat the Conchozoa or Shell-animals.
Fam. 4. Mussel-Kracken—Brachiopoda.
The body is surrounded by a mantle open above, and by two shells; on the sides of the mouth there are two arms.
These animals look exactly like Bivalve Mollusca; they are firmly adherent to rocks, being frequently supported upon a hollow pedicle, which is a prolongation of the mantle. Branchiæ and sexual parts but little known; species probably androgynous—Armkracken.
3500. In the following families the body is free andsacciform, provided with arms or fins, and mostly with eyes upon a kind of head.
These animals have the mouth situated above or in front of the body, and are distinctly separated into mantle and abdomen, while they are frequently surrounded by a shell. They have a kind of head with tentacles or arms, and frequently furnished with eyes like the Snails, or pretty nearly like the Fishes; the sexual parts united and separated. They all row, paddle, or steer themselves about in the sea.
Fam. 5. Snail-Kracken—Pteropoda.
Body mostly gelatinous, sacciform, closed all round and free; fins upon the sides of the neck, with two tentacula frequently projecting from near the mouth; androgynous, naked, and inclosed within a shell.
These transparent animalcules swim about upright in the sea, and wave the fins in this position as rapidly as a butterfly does its wings. Most of them are covered with a spathiform and likewise transparent shell. The branchiæ are placed externally on the body, but are not very distinct. Several species have an appendage in front of the neck, which is obviously a rudiment of the Snail's pad or sole—Flugelkracken.
The Heteropoda appear to resemble the Plantar or Sole-Snails, but the body is mostly gelatinous, and the foot or sole is only compressed to form a fin, so that they can only swim but not creep with it. Many of them have a shell almost like that of the Argonauta. Pterotracheæ—Ruderkracken.
Fam. 6. Typical Kracken, Cephalopoda or Sepiæ.
Muscular animals inclosed within a sacciform mantle, open in front; head furnished with eyes, and surrounded by more than four strong prehensile arms; laminated or leaf-like branchiæ within the mantle, sexes separate; in the body is a nephroidal or kidney-like gland, which secretes a dark-coloured or inky fluid, on which account they are called by us 'Dintenschnecken'—Sternkracken. They are obviously the highest organized Malacozoa, and already remind us strongly of Fishes, partly from their size,partly by their fleshy body, and in part by their perfect organs of vision.
The body is often as large as the trunk of a man; the head being separated from it by means of a neck, has in its interior a kind of cartilaginous brain-case or skull, with externally a pair of jaws resembling a Bird's beak, and with eyes tolerably similar to those of Fishes. Auditory organs are also present, which consist of a tympanic cavity inclosing an otolithe or ear-ossicle; nostrils are wanting. The so-called arms are perfect organs of locomotion, as also useful for seizing the prey, being provided for this purpose with sucking cups, which adhere by producing a vacuum, when applied. In other respects these arms are nothing else but the Snail's sole divided in front into lobes. The ova resemble berries, and hang attached to one another in branched clusters like a bunch of grapes. The Sepiæ possess a remarkable gland, which is complicated with the liver, and secretes a dark brown juice, which has been called ink or sepia; it probably ranks in the significance of the kidneys.
Many are covered with a shell externally, as the Nautili and Argonautæ; but in the common Sepiæ this shell adheres within the mantle upon the back, and forms a straight lamina or plate, which is sometimes horny, sometimes calcareous in its texture. It has been called the "white fish-bone." What is regarded as the dorsal side of the animal is its ventral side, because upon the former lies the pallial aperture and the anus, while the vitelline sac is also inserted there.
In the form of the body, as well as in the circular position of the cephalic arms, the Sepiæ strikingly resemble their antetypes, the Acalephæ and Cirripedia, and their metatypes, the Asteriadæ and Crustacea.
With these animals the second stage or circle through which the Dermatozoa pass, or that of the Sexual animals, is closed. They require only a slight additional grade of perfection, and they would pass over into another class of animals. Thus were the arms to become horny and articulate, they would be Crustacea; had the head anose, and the body consequently a myelon or spinal chord, they would then be Fishes.
SECOND CIRCLE. RESPIRATORY, CUTANEOUS ANIMALS—ANCYLIOZOA.
3501. Body annulate.
Here range the Worms, Crustacea, and the proper or volant Insects.
3502. In this circle a remarkable relation is revealed. If, namely, its classes, orders, and families be compared with those of the two preceding circles, it is then distinctly shown that the present one again commences quite from below, ascends parallel with both these, and transcends them in its highest inmates or members.
As an example of the first case, the imperfect condition of some Entozoa, and their great resemblance to Infusoria, is sufficiently expressive.
The Worms evidently pass parallel to the Mucus-animals, and the Entozoa indeed to the Infusoria, the Red-blooded Worms to the Polyps, but the Holothuriæ chiefly to the Acalephæ, near which they are still arranged up to the present day, although they are articulated, and have an intestine and vessels.
Thus this class traverses the three inferior classes, and consequently imparts to them only the value of orders, or must itself be raised only to the rank of an order, a step, however, which, considering the great number of Worms, would not be suitable or just. The names may therefore remain for the sake of uniformity; only it must be borne in mind that they are of unequal value.
The same relation is exhibited in the Crustacea or Crabs. They obviously admit of being parallelized with no other animals than the Malaco-or Conchozoa. The Entomostraca and Crabs evidently repeat the Mussels, the Aselli the Snails; but the Spiders and Scorpions the Kracken or Cephalopoda. Consequently here also the orders correspond to the preceding classes.
The true or proper Insects transcend the Sexual animals, and therefore conform to the classification of their owncircle, namely, they repeat the Worms and Crabs, and finally mount forth upon their own stage.
The inferior or lower organized animals form consequently two series, viz. the Smooth and Annulate, which in their lower members range parallel, and that indeed after the following manner: