Chapter XXVII: Part III: Biology--Of the Whole in Singulars (14)

3347. Every Sarcozoon, whose nostrils do not open into the mouth, is a Fish. The Siren therefore does not belong to the present class, while the Lepidosiren, having an imperforate nasal organ, does.

3348. The tongue has remained rather an organ of touch and deglutition, than an instrument of taste. The salivary glands are scarcely developed.

3349. But the tongue here appears _for the first time_ in the animal kingdom as a perfect organ provided with muscles, and a lingual bone, as in Man; Fishes are, as regards the development of this sense the _Glossozoa_, Lingual or Tongue-animals.

3350. As Fishes are the repetition of the intestine and vitellus, so they may be termed _abdominal_ or rather _Pelvic animals_. They are an abdomen, unto which are appended branchiæ, fins and head.

They are the repetition of the Infusoria, Mussels, and Worms; in them we meet with mucus, branchial opercula, articulated filaments, and labial cirrhi or palpal organs.

_Class 11. Myozoa, Rhinozoa._

3351. Those Sarcozoa which for the first time obtain true muscles and a perforated nasal organ are the _Reptilia_.

3352. True muscles are red, have a definitely circumscribed outline, and are divisible into head, fleshy portion or belly, and tail or tendon. As such they are found for the first time in Reptiles.

_Thorax._

3353. With the osseous system in Fishes the sexual abdomen was chiefly developed; with the muscular system therefore, as in the present class, the abdomen proper or intestinal abdomen becomes perfectly developed, and the thorax more spacious in calibre.

3354. The thorax is still blended with the abdomen. In Fishes the disposition was already stirring to create for themselves an air-organ; only this was imperfectly attained, since the swim-cyst communicated with the gullet, but not with the branchial arches or larynx, nor with the nasal organ, as in the present class.

3355. Now, if the swim-cyst be symmetrically developed, if it communicates with the branchial larynx and opens through the nose, the aerial respiration is completely attained, and shares its dominion over the body along with the digestive function.

3356. A Fish, respiring through the nose into two swim-bladders, is an Amphibious animal, a _Reptile_.

3357. In the Reptile, however, the thorax is still subordinated to the abdomen. Its lungs traverse the whole abdominal cavity, and its manner of breathing is still similar in character to the abdominal function. The lungs are simply two membranous bladders, like two intestines, and admit also of being voluntarily filled with air like the intestine is with water. This filling or inflation of the Reptile's lungs takes place also by the abdomen being expanded at the same time that the mouth is closed by the muscles of the fauces, and is therefore a true process of deglutition.

3358. Their inspiration is still therefore fish-like in character, excepting that the air is drawn in by the nostrils; the respiratory process, however, and the respiratory organ is constituted as in the perfect air-breathing animals.

3359. Reptiles may therefore be called _Abdominal animals_, while the Fishes are Pelvic animals.

3360. The metamorphosis of the branchial arches into larynx is placed beyond doubt in the Reptiles. The anterior branchial arches frequently unite with the lingual bone, whereby the latter obtains several cornua.

3361. The thyroid gland also makes its appearance here for the first time, while the branchial vessels separate from the arches. Fishes have therefore no thyroid gland.

3362. The circulation is complete. The venous and also the arterial blood enters the heart. But both kinds of blood are still mingled with each other as in Fishes. Yet already, through the direction and arrangement of the cardiac orifices, provision seems to be made for their separation.

3363. The rationale of this mixture of the blood appears to reside in the fact, that many of these animals, and probably all of them in the ovum state, breathe by branchiæ. (This proposition, which was announced in the 1st Edition, 1810. § 305, and there based upon the transitional stages traversed by the animal classes during embryonic development, has since then been raised to a state of certainty.)

3364. The mixture of the blood takes place through an opening in the septum separating the two cardiac ventricles, and which corresponds to the foramen ovale of the foetus. The heart of Reptiles is therefore a persistent foetal heart.

3365. Without doubt, however, the arterial blood only enters the left heart, while the venous remains in the right, to be thence driven into the lungs.

3366. In other respects the foramen ovale is not a true opening, but a bifurcation of the vena cava, one branch of which passes into the right, the other into the left ventricle, as I have demonstrated in the 'Beyträgen zur Anatomie' (Frankfurt bei Wesche), in treating of the calf's heart.

3367. There are generally no foramina in the body, but only fissures without orifices.

_Abdomen._

3368. The digestive organs are pretty similar to those in Fishes, as is exemplified by the intestine, liver, and spleen; the digestive process is, however, more energetic, and frequently aided by venom or poison.

3369. The sexual parts are perfect. The first true testes and ovaria have originated. The tegumental formation has consequently passed over at the extremities into a glandular, because the vascular system preponderates. Even in the highest Fishes, such as the Rays and Sharks, the testes and ovaria are still not developed to the extent which they are in Reptiles.

3370. In the female the oviducts pass together as complete cornua into an uterus. In the male the seminal ducts are still indeed separate, yet the two bodies or crura of the penis are frequently developed, and continue separate in the Serpents and Lizards, but are connate in the Tortoises.

3371. The kidneys are distinct and symmetrical; their ureters usually unite into a large urinary cyst. Thus, the sexual lung is also significantly developed.

3372. Many of these urinary bladders split, as in the Tortoises, into two cornua. This is the form under which the cyst again occurs in Birds, where its two cornua have been incorrectly termed coeca, but the urinary cyst rectum, because the intestine opens into it.

3373. In Reptiles also there is a cloaca or sexual orifice, into which all the sexual apertures meet together.

The ova of Reptiles possess a vitellus and albumen, and are surrounded by a membranous or sometimes by a calcareous shell.

3374. Hence Reptiles have originally also a coecum, but it has for the most part disappeared; like its antetype the vitelline canal, which is so small in most Fishes and Birds, as to be scarcely distinguishable.

The tail projects from the body, and is rather trailed after the animal, than enabled to assist the body in its motions, as in Fishes.

_Senses._

3375. Many Fishes have only a vertebral column without lateral bones; in the Thoracic animals this deficiency can hardly occur any longer, although we are not, on the other hand, to expect any great amount of perfection to be attained by these parts. Reptiles have osseous ramules, whether such be ribs or true feet; the Serpents have indeed only ribs, but these exist in great numbers; in the Frogs, on the contrary, ribs are wanting, but they have limbs.

In no Reptile do fin-rays occur; consequently, there are no peculiar bones as in Fishes.

3376. In Reptiles the limbs themselves are in a varied or undetermined state, although they constitute a class in which the formation of true muscular limbs is decided. In Reptiles the toes appear for the first time.

3377. As regards the tegument, it quite corresponds with that of the Corals, Snails, and Crabs, of which the Reptiles are a repetition. In some cases it is slimy and naked; in others Mussel-shells originate, as in the carapace of the Tortoises; the scales, scutes, and claws of Serpents and Lizards repeat the rings and scutes of Crabs.

3378. The head has separated itself more from the thorax, the eyes and ears being much more perfect; as regards the latter organs the cranium is always perforated, in the former there are eyelids.

3379. The eyes have still no power of free motion, and the eyelids are as yet very imperfect. It is principally the lower eyelid which closes, while in Mammalia the upper one is the most developed.

3380. The external auditory meatus is notwithstanding usually covered by integument, the auditory ossicles are mostly blended into one, which projects above the skull; the cochlea is wanting.

3381. Reptiles produce sounds for the first time through the lungs; they have voice, but as yet no song.

3382. The nose, however, gives the finishing touch to the head. It has not only opened as a vertebral canal in front, but also as a thoracic cavity posteriorly into the mouth, which was not the case in Fishes. The open nose is the æsthetic character of Reptiles, just as the red muscles are the characteristics of the anatomical systems. The Reptiles are _Rhinozoa_.

3383. The tongue takes a higher rank than in Fishes. It is throughout soft, fleshy, and smooth; but in most species is still slit into two, which reminds us of a similar condition of the penis.

3384. The teeth are in these animals more like digits than in Fishes. While here they consist for the greatest part of front teeth, and are therefore associated with the intestine, in Reptiles they are mostly lateral, and thus true maxillary teeth, which are annexed to the salivary system. With this special dental formation the saliva is also more active; it is a rapidly fatal poison.

3385. The poison-teeth or fangs have likewise a groove, which can be regarded as the continuation of the salivary duct.

_Class 12. Neurozoa, Otozoa._

3386. Those Sarcozoa, whose nervous system is for the first time perfectly developed, and whose ear is open externally, are the _Birds_.

3387. The completion of the nervous system is the brain; now the brain defines or determines the head; the Bird is, properly speaking, the first Encephalic animal.

3388. In the Bird the head has for the first time, and that indeed suddenly, freed itself from the trunk, and been placed upon a long neck, far removed from the thorax. In no class are there such long necks and so many cervical vertebræ to be found as in Birds. They can be therefore called also Cervical animals, as the neck is not simply present, in order to render the head independent or self-substantial.

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 therefore _Encephalic 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-cyst; 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 respiratory system 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 than _one_ feather, 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 the _Otozoon_.

_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, and thus 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.

_Class_ 13. _Aistheseozoa._

3426. An animal with all its organs of sense perfectly developed, is a _Thricozoon_.

3427. The nervous system emerges at length freely above the other systems, and it is no longer its mass, but its _organs_ which 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 a _fleshy 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 a _tegumental 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 can view 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 undergo modifications. 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 with _tegumental_ muscles 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 the _Thricozoa_.

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 a _fur_--_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 in many 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 becomes _animal_, 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 also _Mastozoa_ or 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 a _furred 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.

D. ORDERS AND FAMILIES.

3456. Had the names been given in strict accordance with rank; then the class-divisions, which correspond to the circles, would have been called _Orders_.

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 time _Cohorts_, 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 the _first class_, or Infusoria proper, correspond the _Monades_.

To the _second class_, or Polyps, the _Rhizopoda_.

To the _third class_, or Acalephæ, the _Rotifera_.

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 a multi-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 with _capillary tentacula_ around the mouth, as the naked Polyps, Tubulariæ, Sertulariæ, and Cellulariæ.

The others have true ciliated _tentacular rays_ surrounding 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 ordinary _tentacula_, 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 the _naked Polyps_ are 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. The _Cellulariæ_ cannot 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.

The _Radiated Polyps_ or 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 foetal 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, or _Physaliæ_, Rippenquallen or _Beroes_, Hutquallen or _Acalephæ_.

3483. The _Physaliæ_ are without doubt the lowest, being only giant Infusoria; the _Beroes_ are allied through their simple bodily cavity, to the Gorgoniæ; the _Acalephæ_, 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--_Medusæ_.

3485. The _first_ have 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. The _second_ family 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. The _third_ have, as a general rule, one central mouth 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 foetal 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 only _one_ order. The want of a fourth family and so on, proves that the development of these animals does not pass 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.

_Order_ 1. _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 respiratory tubes 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._

Only _one_ occlusor 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 appearance for 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. Dioecious.

_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; they _must impregnate themselves_.

_Order 2. Conchozooid Snails--Dioecii._

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 proper _Cylindrical 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._

The _Salpæ_ are 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.