3219. Every thing else in the Snails is arranged in accordance with these fundamental organs and forms.
The cephalic portion of the intestinal canal is indicated also by muscular fibres. The pharynx and the mouth can contract and expand, seize and bite off; the former frequently admits of being protruded and retracted as a fleshy proboscis with perforating maxillæ.
3220. Since the muscular fibres are only tegumentalfibres, and therefore lie within cavities; they thus act like as in the feet of Insects.
The tentacula of many Snails are moved like the feet of Insects; but as they are not horny, but soft, they are turned either inside out or "vice versâ." The oviduct and seminal duct or penis follow the same mode of formation. They are likewise everted and inverted.
3221. These members of the Snail are true Insect-limbs that have remained soft, and are thereupon susceptible of inversion and eversion. Were an Insect's foot soft, every one will admit that it would then yield so as to become inverted, if the fibres pulled upon it. The limbs of Insects have thus only become stiff, and are thereby Snail's horns that resist inversion. All these members are teguments, and give the lie only unto limbs; for it belongs to the essence of a limb, that it be dense.
3222. That which suffers eversion or its converse is no limb, but only a sheath, a prepuce. Nearly the whole Snail is but a prepuce, a "membrum virile" or "verge."
3223. There is no class of animals, in which the testes and penis are found so disproportionately developed as in the Snails—Orchitic, Penes-animals.
3224. The vascular and nervous systems are related pretty nearly as in the Mussels. But the heart is fleshy and has, by reason of its unilateral or single branchia, only one auricle also.
3225. The Snails repeat the Corals in the cylindrical form of the body, the tubular-shaped shell, and the return of the intestine upon itself towards the mouth, as in many Corallines.
3226. In them also the organ, which virtually corresponds to the kidney, appears to be astir, namely, what has been called thecalcareous gland, situated within the branchial cavity, and which opens not far from the anus.
Class 6. Cardiac, Nephritic Animals.
3227. Hitherto there has been found only a single "cardia," namely, the left or arterial heart, which, receiving the oxygenated blood from the branchiæ, propelsit to all parts of the body—for the purposes of nutrition. But now also the right heart suddenly makes its appearance, which drives the blood into the branchiæ—for oxygenation. This must doubtless be regarded as a higher development, especially since, as I have shown, in the higher animals as well as in the embryo, the right heart is first perfected subsequently to the left.
The Conchozoa with a double heart are the Sepiæ or Cuttle-fishes. These are in consequence correctly calledCardiac animals, and must be regarded as the fundamental form of this stage.
With this completion of the heart other structural changes, which probably stand in intimate connexion with it, appear. In the Snails indeed a kind of renal organ, or what has been called the calcareous gland in the branchial cavity, has been already shown to exist. Whether the shoulder-gland in the other Mollusca belongs also to the members of the present class, may be left undetermined. This kidney, like other vegetative organs, pours out its secretion quite involuntarily. In the Cuttle-fishes it is, however, combined with an organ, by means of which it can discharge its fluid, or the ink, voluntarily as in the higher animals. The kidney or ink-gland with the ink-sac is therefore characteristic likewise of the Sepiæ, and admits of our calling these creaturesNephriticorRenal animals.
At the same time the whole form of the body is altered; it becomes cylindrical, and is provided upon the ventral aspect with neither a muscular keel nor sole, whereby it might glide or shove itself along; thus herein also a resemblance is manifested to the higher animals.
This motionless body is on the contrary endowed with independent organs of locomotion, namely, with fins or arms, which are wanting in the Snails and Bivalve Mollusca. The labour of motion is consequently removed by the organs which minister unto it from the body, and thus we trace another similitude to the higher animals, which transport their body from place to place by wings or feet. These animals can be therefore calledCylindrical Snails, out of contrast to theSoleandCarinate Snailsor the Bivalve Mollusca.
Closely allied now to these cylindrimorphous Conchozoa are all those Mollusca in whom the keel (carina) or sole is wanting; i. e. such snail or mussel-like animals, which either cannot transport themselves at all, or effect this by means of fins or podoidal appendages, in short all that have been called Snails, having no sole, and all supposed to be Mussels, but without a keel.
Now, the Heteropoda or Pterotracheæ and the Pteropoda or Clionæ have projecting processes which act like fins.
The Brachiopoda or Terebratulæ, though unendowed with the power of locomotion, have, as their first name implies, arm-like organs.
The Cirripedia or Lepades, being likewise without the power of continuous motion, possess podoidal or foot-like appendages. In both these families, however, these appendages are nevertheless true motor organs; for by means of them they seize their food, an act which hitherto has been seen to take place neither in the Snails nor Bivalve Mollusca.
Lastly, the prehensile organs dwindle down into mere filaments or small lobes, but the body always retains its cylindrical form without keel and sole, as in the Ascidiæ or Meerscheiden.
In the Salpæ only the cylindrical body is left, unto which appendages are still, and not rarely either, attached, serving them wherewith to lay hold of each other. In accordance consequently with their external form all these animals appertain to one class along with the Cuttle-fishes. I call themKracken.
The renal organs are still not to be found in all of them; the structure alone of the heart agrees essentially, despite of its simplicity, with that of the Cuttle-fishes. In the Ascidiæ, simple as well as compound species, it is indeed but a single, though muscular pouch. Now, this pouch drives the blood alternately, at one time into the branchiæ, at another backwards intothe body, and is thus in the first act a venous or right heart, in the latter an arteriose or left; consequently, according to function this single pouch is compounded or made up of the two hearts.
The branchiæ deviate entirely from those of the Mussels and Snails, and exhibit a very complicated structure; in the mussel-like families they present the form of a trellis-shaped sac, as in the Ascidiæ, or that of filiform appendages to the feet, as in the Cirripedia, or they are funiform as in the Brachiopoda. In the Pteropoda they are very varied; in the snail-like Heteropoda they are mostly pectiniform or tuft-shaped; in the Sepiæ or Cephalopoda phylliform or fin-shaped.
The external character ccommon to the whole class is thecylindrical body, unto which may be aptly conjoined the possession of special organs of motion; whether such organs be prehensile in function, media of support, or veritable instruments of progression.
The snail-like Pteropoda, Heteropoda, and Cephalopoda, have a head, but this is wanting in the mussel-like Salpæ, Ascidiæ, Cirripedia, and Brachiopoda.
THIRD CIRCLE. RESPIRATORY, CUTANEOUS ANIMALS.
3228. Respiratory animals are Dermatozoa with a predominating system of respiration.
Now, the respiratory system is the tegument, which here then must attain the highest pitch of perfection.
This again takes place through the increased process of oxydation, which produces induration of the parts.
The vessels, which surround the tegument, must nourish this portion of it to a greater degree and render it harder or more compact than any other, whereby alternating expansions and contractions thereof originate, in other words, the structure of the trachea.
3229. The whole body of the Respiratory animals becomes a trachea, a series of rings. The Respiratory are therefore theAnnulate animals.
The rings are to be regarded as cysts, which are mutually juxtaposited or repeated, not being insertedwithin each other as in the preceding animals, but behind each other, so that the present circle consists of multiplied Cystic animals.
3230. The Annulate animals must represent the developmental stages of the tegument, while the viscera make a retrograde step—Tactile animals.
3231. The tegument has two functions: it is an organ of respiration and of general feeling or sensation. In both cases it passes through three stages of development.
It is either entirely a branchia, i. e.reticularin character; or the branchiæ become individualized in certain situations and partly horny, constitutingbranchiæproper; or finally, the tegument is converted into an air-breathing organ,tracheæorair-tubes.
3232. It either feels with its whole surface, or bypapillæ; or the branchiæ change into hornyfeet; or lastly, into alary appendages orwings. The Ancyliozoa consequently divide into Reticular or Papillary animals; into Branchial or Pedal, and into Tracheal or Winged animals.
3233. As the arterial character preponderates in these animals, so do the venous organs, especially the liver and renal structures, retrograde.
3234. The body is now an intestinal and tegumental body with predominating respiratory and sentient organs; here therefore sensitive papillæ, antennæ, feet and wings, appear in abundance.
3235. With the retrogression of the viscera, the glandular structure also and large proportional bulk of the sexual parts disappears. They assume the form of the intestine and tegument, i. e. become tubes.
The spawn like the milt consists, as a general rule, of only two long membranous tubes, running near the intestine.
3236. The external sexual parts belong to the sense of feeling and follow the developments of the tegument; they make their appearance as antennæ, and are usually accompanied by foot-like accessory organs.
3237. The nervous system in like manner accompanies the tegument. It consists of two gangliated cords passing along the ventral surface.
3238. As the maxillæ are only repeated feet, so they are rarely wanting, and are, like the latter, disposed after the fashion of scissor-blades. The same holds good of the antennæ; they are mostly in pairs, and consist of a series of rings projecting from the head.
3239. The eyes are usually present, but only as tegumental organs, or placed upon the points of the antennæ.
Class 7. Reticular or Papillary Animals.
3240. The repetition of the Intestinal or Vascular animal, taking place under the dominion of the respiratory system, must be accompanied by the vascular system. The tegument is a vascular, a branchial membrane, abranchial networkorskin.
3241. A body with predominating tegumental and intestinal system, is cylindrical. It can only become gross or lump-shaped, if the glandular viscera, such as liver, ovarium and testes, get the upper hand or prevail.
3242. A tegument which appears as a branchial membrane, is annulate or ringed.
3243. An animal, having an annulate respiratory membrane without annulated feet, is aWorm.
Upon the lowest stage the vascular system is still similar to that of the Vascular animals; its blood is a colourless fluid—White Worms, Entozoa.
In order to be a Worm, it is sufficient to have an annulate tegument. Even if the intestine be wanting and the tegument supplies its place; the character is nevertheless complete. Here it is the skin, which digests, while in the Intestinal animals it is the intestine, which digests and breathes. Since it is here the tegument, which undertakes the offices of the whole body; the vessels, liver, and salivary glands are wanting unto the intestine.
The sexual parts are also frequently arrested and the ova appear to originate in the tegument.
Many undergo division without injury to themselves; yet the detached portions do not become again entire animals.
In most of them, however, the sexual parts of both sexes are present, being associated with, though separate and distinct from, each other; those of the female mostly opening upon the sides of the body.
As being Dermatozoa, they have for the most part special organs of sensation around the mouth, under the form of papillæ, filaments, spines and cups. The nervous system, wherever it is to be met with, consists of a ring surrounding the pharynx, and of a double ganglionic cord lying along the ventral surface of the body.
3244. Upon a higher stage of development the arterial system gains the preponderance, and the blood becomes mostly of a red colour—Red-blooded Worms.
3245. With the arterial the fibrous system also makes a more decisive appearance. The tegument is a fibrous tunic—it is itself an artery. All Annulate animals with a fibrous tunic, which can consequently contract, belong to this class, whether too they have red blood or not, like the Holothuriæ and Star-fishes.
3246. The Lumbricales or Earth-worms and the Hirudines or Leeches respire obviously through the whole tegument, though a special organ of respiration does begin to be evolved, in the first family in the "saddle," in the second in the lateral vesicles or cysts.
3247. In others the branchial vessels make their appearance above the level of the tegument as filaments or ramules, and are arranged in two rows, as in the common Sea-worm and in the Nereides.
3248. Lastly, they accumulate about the neck or head, as in the Amphitrites and Serpulariæ.
3249. There are also Worms which respire only through the intestine, its vascular system being bathed on all sides by water, as in the Aphroditæ. This water becomes, as it would appear, simply imbibed by the tegument in Thalassema, but through an opening at the anal extremity of the body in the Holothuriæ.
3250. These Worms have also no liver, or at the very best only traces of that organ, by reason of the preponderance of the arteries.
3251. Papillæ or sensitive filaments gradually sprout from the external branchial filaments, lie along the sides of the body, and are the prelude of the feet; as in the Nereides—Papillary, Filamentary animals.
3252. Others of these filaments become horny and appear as setæ or bristles, placed somewhat similarly to the above, as in the Earth-worm.
3253. Mouth and head are more perfectly developed than in the Entozoa. The first can readily expand and contract, frequently protrude the pharynx like a proboscis or tube, and not unfrequently has manducatory pincers, like as in Insects.
3254. On the head there are mostly annulate tentacula with muscular fibres, and frequently simple eyes.
3255. In those species which draw the water itself into the body and use it for the purposes of respiration, the formation of the mouth has risen higher, and the pharynx been provided with maxillæ, in number five or ten—Echini, Holothuriæ. These maxillæ form in themselves a peculiar skeleton around the pharynx, which is ranged circularly instead of by pairs.
3256. The nervous system is directed according to the relations of the tegument and intestine. It forms two ganglionic cords running along the ventral side of the body, and, where it makes with the nerves going to the maxillæ a ring around the pharynx, corresponds to the pharyngeal or pneumogastric nerves.
3257. In reference to the sense of feeling it may be said, that the Worms were those among the Sensitive animals, which feel by the whole tegument or body. Their body itself is a tentaculum.
3258. The sexual parts are likewise intestini-and dermiform, not glandular in figure like the ovarium and testis of Mussels and Snails, but tubular, as in the Entozoa. There are usually two oviducts and two seminal tubes to be found.
3259. So far as we are acquainted with the Red-blooded worms, they are androgynous, at least as regards the Earth-worms and Leeches, and their sexual parts are indeed tolerably symmetrical; yet they do not open posteriorly, but far forwards on the ventral side of the body, this being the case with even the male sex-organs.
Class 8. Branchial, Pedal Animals.
3260. The representation of the Cutaneous animals is not yet the entire completion of the tegument. It attains a higher grade by separating in accordance with the visceral systems, and in the conversion of the branchiæ into sensorial organs or feet.
The branchiæ endeavour to separate self-substantially, and form a body of their own. The branchial body is the thorax.
By this attempt, the abdomen originates "per se" as the body of the intestinal and sexual system. The branchiæ upon it are arrested or stunted. In like manner the body of the nerves separates itself from the thorax and becomes head.
But meanwhile this separation is only imperfect; the head and thorax, if otherwise distinguished by their size and the feet, are for the most part connate; abdomen and tail are usually fused together, and only to be recognized as distinct by the limbs or members.
With this greater division of the body each division of it obtains its articulation into rings; but they will be hardened by virtue of the separation of the branchial network, or will become horny—Horny animals.
3261. With the conversion into horny texture of the body, its branchial filaments or tentacula must undergo a similar change, and divide likewise into rings like the general or bodily tegument.
Annulate, horny branchial filaments, are feet—Pedal animals.
A part of the branchiæ remains hanging to the feet, mostly to their basal joints, and is supported by animal motor members or limbs; the respiration becomes voluntary—Branchial animals.
The Annulate animals, having branchiæ and feet, are theCrustaceaorCrabs.
The branchiæ and feet are, of course, most largely developed upon the thorax.
Those upon the abdomen continue small, and those upon the tail or sexual body dwindle in size and change into other organs, such as fins, sacs, filaments, pincers.
3262. The number five of the branchiæ is also exhibited in the feet. There are mostly five large pairs of feet on the thorax, and as many small ones on the abdomen, as in the Crabs.
On the tail they appear more dwindled in size, and are frequently reduced to a smaller number.
Each part of the body has properly five rings; and these parts being the thorax, abdomen and tail, there are thus fifteen rings in all.
In the Crabs it is distinctly demonstrated that the maxillæ are nothing else but feet; there are therefore for the most part, after taking into account sundry arrests and coalescences, five pairs of maxillæ also.
The Crabs have usually two pairs of antennæ, whose signification is unknown; one pair is probably the elongation of the ear.
All Branchial animals have eyes, frequently too supported upon articulated pedicles.
They have a double nervous cord upon the ventral surface of the body.
They have, like the Mussels, a heart upon the dorsal aspect, and arteries with veins.
The intestine opens into the apex of the tail, and is surrounded by a liver.
The sexual parts still open for the most part on the thorax, and indeed by two orifices, as in the Worms.
There are no more androgynous or bisexual beings in the present class.
In some few the branchiæ already enter the body and become air-tubes, as in the Scolopendræ, Spiders and Scorpions.
The Branchial animals repeat, as being the secondclass of their circle, the Corals and Snails; their "quasi" coat of mail is therefore harder, often richer in calcareous ingredients, and, in addition to this, lies frequently upon the thorax or branchia as a special testa, called the scute or shield.
Class 9. Tracheal, Alary Animals.
Annulate animals, whose branchiæ have undergone a partial conversion into tracheæ and into wings, are theInsectaproper orFlies.
3263. A Worm with feet, tracheæ and wings, is anEntomonorInsect.
3264. The first separation takes place in respect to the three tegumental segments of the body, the abdomen, thorax, and head. All three are, in the Insects, more separated from each other than in the Branchial animals, and united together usually by a narrow tube; even in cases also, where they are connate with each other, they are still easily recognized by respect being had to size, form, or appendages.
Every Insect is divided into three segments. In the abdomen are the organs belonging to the Worm, such as the intestine, and a fatty body which appears to be an analogue of the liver, a dorsal vessel, tubular sexual parts and air-tubes (tracheæ), but nothing else.
The abdominal feet now disappear entirely, and even the number of thoracic feet diminishes, owing, doubtless, to the production of wings.
3265. The thorax alone is reserved for the limbs or locomotive members. It never carries more than three pairs of legs and two pairs of wings. Of the viscera, it contains nothing but the pharynx, while in the Crabs, important intestinal organs and even the liver, are situated within its cavity. It is in Insects therefore nothing else than a medium of support to the respiratory organs which have become limbs. Hence the thorax never has more than three rings, namely, one for each pair of legs. The wings invariably stand upon its two posterior rings.
3266. Since the limbs of the Insect are only the lateral filaments of the Worms, which have become hard and consequently hollow; they are as such not to be termed true feet, but are only to be compared with branchial arches or ribs; a step by which their greater number also admits of being understood. They are not to be compared with our feet, but unto the toes, which have been separated from each other as far as the rings of the body. The Crab has properly five thoracic and five abdominal toes. All its thoracic feet taken together are only equivalent to our hand.
The feet of the higher animals are only Insect-feet connate or coalesced.
3267. In other respects they already typify or prefigure true limbs, as well from their position as by the division of their joints. A perfect beetle's foot divides exactly like the limb of Man, into femur, patella, tibia, tarsus, and phalanges. These parts of the leg must not, however, be so absurdly divided and named, as has hitherto been unfortunately the case in our systems, where the femur has been called coxa, the patella trochanter, the tibia femur, while the toes have been lumped under the name of tarsus. (Ed. 1st, 1811. § 3087.) The regular number of the toes or tarsal joints is five, so that they correspond to our digital phalanges, to the metacarpal, and the anterior carpal bone.
3268. The wings are the branchiæ of the Mollusc that have been set free; they are placed therefore upon the back and are four in number. In many Insects there is still a pair of wing-like scales in front of the four wings, as in some Lepidoptera. They perhaps correspond to the shells of Molluscs, are branchial opercula.
It is only from this point of view that the structure of Insects admits of being fully understood; and apart from this it is absolutely devoid of all analogy. Thus it is possible for only six legs to take their origin from the thorax in the direction downwards, and nevertheless for there still to be wings upon the dorsum or back. The wings of Birds are by no means homologous to the alar appendages ofInsects; they are, as is well known, the anterior members themselves, and there is no longer therefore in the Bird any feet attached to the thorax below, as in Insects. Besides, if the wings did not signify arms in the Bird, then it must have four legs. Thus in the Insect the wings could not also mean feet.
Their structure also speaks in favour of our view of the Insect's wings. They are known to be completely traversed by respiratory tubes, are true, or only desiccated, branchiæ—aerial gills. (Ed. 1st, 1811. § 3088.) Wings and feet are dependent from the same ring of the body, and are thus like the branchiæ and feet of the Crabs. Let the Crab's branchiæ elongate and dry, and they will thus be wings.
3269. Since the wings are newly eliminated organs of the sense of feeling, so are they here characteristic of the animal, and are consequently of greater importance for the purposes of division and arrangement than the organs of the head, which in all the lower animals is only an apparent head, and cannot therefore serve to characterize groups, &c.
3270. That the tracheæ in Insects have been developed out of the branchiæ by saccular inversion, is a fact displayed in a particularly distinct manner by the Scorpions and Spiders, who still possess at bottom internal branchial laminæ, unto which, however, air instead of water finds its way. It may be said, that with the general conversion into horny texture, the arteries of the Mussels were transmuted into internal tracheæ, and the branchial flabellæ into external organs. Would we interpret the body of the Insect in a strictly philosophic sense, the parts must then receive very different names to what they now bear. Properly speaking, in our own species the thorax has no limbs, but only the neck. The upper limbs are not lungs, but branchial organs, and it is the cervical vertebræ, from between which nerves are sent off to the arms, for it is just upon the neck also that the branchiæ have been left. What is termed therefore the thorax in Insects, would be properly their neck. Theirabdomen would consist accordingly of thorax and abdomen, and it is this also, which carries on the principal share of the respiratory process. It therefore consists generally of ten rings, and has ten pairs of spiracula, namely, twice five, for both thorax and abdomen.
Or again, the abdomen may be regarded as an intestinal and sexual cavity, and the thorax may be left with its own name. In that case there would be five spiracles for the sex, five for the intestine, and perhaps only two for the thorax.
Would we proceed yet further; the head can then only be viewed as pharynx, and consequently as neck.
3271. In most Branchial animals that live in the water, a perfect circulation is present, because, by reason of their feeble amount of respiration, all the blood is not consumed. This is also the case in the young of air-breathing Insects, so long as they may have to grow. But when they have ceased to do this, so strong an amount of tension emerges in the circulation, owing to the increased respiration of air, that blood remains but in scanty quantity to be carried back by the veins, and the arteries now for the most part convey the air in a pure state, namely, uncombined with blood, as in the higher animals.
3272. As the air-tubes pass to all parts of the body, like the arteries whose place they now supply, so does the nutritive juice become everywhere oxydized and converted into parenchyma or tissue. The nutritive juice doubtless transudes at once through the intestine and penetrates to all parts, as in the Plants.
3273. Of the vascular system nothing at last remains but the dorsal vessel, whose ramifications appear to disappear entirely. According to its analogy with the Crabs, Scorpions, and Spiders, it is the aorta. It appears, as if in Insects the circulation dies off from the living body.
The whole Insect is an air-organ, an aero-vascular stem. All the organs respire directly, such as the intestine, the motor fibres, nerves, sexual parts, andwings. There is no part unto which tracheæ do not pass, and in this respect completely resemble the arteries of other animals.
3274. The intestine is invariably furnished with an anus, and that too situated quite posteriorly. It is usually expanded into several stomachs and has appendages, almost as in Fishes, which virtually correspond to the abdomino-salivary or pancreatic gland.
3275. The salivary ducts open into the mouth, and thus as in the Snails and Kracken, whose similar structures they repeat.
3276. Whether what have been called the biliary vessels are what the name implies, and really convey bile from the fatty body to the intestine, or whether they are lacteal vessels and discharge their fluid near the rectum into the dorsal vessel, does not yet admit of being determined. They have been thought to constitute an urinary apparatus; only certain cysts which occur in connexion with the sexual parts, appear rather to correspond to the latter.
3277. The nervous system consists, as in the Worms, of two ganglionic ventral chords.
3278. In the head, the feet again, and probably also wings, undergo repetition. This repetition is nowhere so distinct as in Insects. He who can still entertain any doubt of the maxillæ being arms, let him resolve to descend into the Insect-world, and he will become in place of a sceptic, a believer. (Ed. 1st, 1811. § 3095.) What have been called manducatory pincers move outwards as well as the legs, and seize like arms, are only arms. Their gripe takes place in the lateral or horizontal direction, and resembles that of scissors or shears.
3279. Where, moreover, there are three pairs of legs on the thorax, we find also three pairs of maxillæ, namely, an upper and lower maxilla, and a labium or inferior lip, which consists of the same parts as the maxillæ, only they are united by tegument.
3280. Where there are five or more pairs of legs on the thorax, as in the Crabs, there also are found as many pairs of maxillæ.
3281. Upon these maxillæ, palpi are likewise situated, which are probably nothing else than what has been termed tarsus, thus repeated in the head also. They are only arrested upon the upper maxillæ or mandibles. (Ed. 1st, 1811. § 3096.)
3282. The wings appear to be repeated upon the head as antennæ. Thus the head also is in the Insects a perfect trunk.
3283. Upon the head there is nothing more than the eyes. They have also become horny in texture, whereas before they were completely membranous, as in the Snails.
The eyes have been subordinated to the sense of feeling; they are nervous papillæ placed beneath a transparent tegument upon the apex of a tentaculum.
Insects therefore have a number of eyes; they stand either separate, as in the Worms, and are then called simple eyes, or they are crowded together, constituting compound eyes.
3284. Of the other sensorial organs a papilliform elevation in the pharynx is frequently exhibited as a tongue.
3285. Ears are found in the Crabs at the root or base of the antennæ, or in them there is only a tympanic cavity with an ossicle inclosed within; in the Insect there is nothing of the same kind. But meanwhile, since many species attract each other by means of sounds, they must thus possess the faculty of hearing. The antennæ therefore probably correspond to the auditory conch. The auditory conch of the Mammalia ranks also in the signification of the hand, and thus of the organ of feeling.
Nevertheless the antennæ may be transformations of the wings. The auditory ossicles are indeed members which have originated from branchiæ. Probably the antennæ are the auditory ossicles themselves which have emerged outwards, as in the Fishes and Reptiles.
There is no trace of a nose; nor can there be any, for it is the anterior orifice of the vertebral canal, and this iswanting in all lower animals. A noseless animal is an inferior or Tegumental animal.
3286. The sexes are separate, because they are Air-breathing animals and perfectly symmetrical in form. The ovi-and seminal ducts are likewise symmetric and in pairs. The ovipositors and penes are perfect, as in the Snails, because they can be shoved forwards, but not everted as in the latter.
3287. The position of the sexual parts at the posterior extremity of the body has been permanently established, with exceedingly few exceptions, as in some aquatic Insects.
That they correspond to the head, or are imperfect cephalic organs, is most distinctly shown in the Insect. They are usually environed by valves, pincers, and filaments, which resemble maxillæ and palpi.
3288. The Ovum-animals multiply by division, by granules or gemmæ, i. e. shoots, the Sexual animals by membranous ova, the Arthritic animals by horny ova. These last, or egg-shells, are hard, and frequently also so strung together or laid by the parent upon each other as to represent the annulate body of some Insect.
3289. In the ova of the Dermatozoa or Tegumental animals the vitellus only appears to exist, being without albumen, which first seems to make its appearance along with the animal systems. As the animal separates into higher and lower substances, so also does the ovum or microzoon. The simplicity of the Tegumental animals has been prophesied or foretold in that of their ova.
The Insecta, as being the third class of their circle, repeat the Acalephæ and Kracken. With the last they bear much resemblance in form and in their motor organs.
3290. Would we arrange the Worms along with the spiral vessels or ducts, the Crabs with the woody rings in the stem, we must term the Tracheal animals foliage or leaves. Their wings are pinnate leaves, and among the Orthoptera many occur which, as well in the form of the body as of the wings, appear as if they had been justliberated from the Papilionaceous tree. The tales or stories, about leaves changing in the torrid zones into Insects, are not without meaning; for poetry is none other than the Ideal of natural history.
Metamorphosis.
3291. We now proceed to retrace our steps. The Insect is a Tegumental animal represented in limbs. There can be therefore present in the Insect no other development than in the Cutaneous animal, which works itself up into the Branchial and Tracheal animal.
The Insect passes through three stages prior to its attaining the adult or perfect condition. It is at first Worm, next Crab, then a perfect, volant animal with limbs, a Fly.
3292. The representative passage of the Insect through the preceding classes in the course of development, constitutes itsmetamorphosis. Thus the Insect's metamorphosis obtains a meaning and an explanation. Upon the whole, the history of every kind of pregnancy is none other than the passage which takes place through all the animal classes, as I have first represented in my book upon "Generation" (Von der Zeugung, 1805); but in no class of animals are the periods so dissevered or drawn apart as in Insects. It therefore comes to pass that these animals are the equivalent transcripts or copies of a system common to them and the preceding animals.
3293. The Worm is the first condition of the Insect. It is represented, by the larva, which, according to its diversity of size, is called maggot, caterpillar, grub, &c.
3294. The larva is only a Cutaneous and Intestinal animal. It knows of nothing else but eating like the Worm; it has no sexual function, no lust, nor pain; it can scarcely move; in many the feet are wanting, as in the larvæ of Flies, which thus resemble the Entozoa; many have a crop of lateral papillæ, like the caterpillars, which resemble the Nereids.
3295. The change into a nympha, chrysalis, or pupa,commences with the horny induration met with in the Crab, and in the higher organized kinds of Snail. The pupa is the embryonic Crab or its antetype, it is the Snail in its shell.
3296. In the third condition the Insect makes an advance above the branchial condition, and casts aside the Snail's or Crab's shell; and is then the perfect Insect, theFly.
3297. The metamorphosis is accordingly the embryonic transition of the Insect, after extrusion from the egg, through the three classes of its circle. In the ovum state it only passes through that of the Intestinal and Sexual animals.
3298. This is a retrospective proof that the higher animals also pass in the ovum through the condition of the lower animals, but after birth through the classes which directly precede them.
What holds good of the Insects, does so also of the preceding groups of animals, although in a less degree; the higher class of each circle still passes after birth through one or other of the inferior classes.
Thus, the Acalephæ first appear under the form of Infusoria; next change into Polyps, and then obtain for the first time the form of the perfect Acalephæ. The same phenomenon occurs in the naked snails or Slugs. They have, when freshly hatched from the egg, a small mussel-like shell, which they lose at a later period.
The Echini or Sea-urchins, which I believe ought to be ranged with the Kracken, also pass through a metamorphosis.
Finally, it is well known that the Crabs also are subjected to a metamorphosis. Their first condition must be regarded as that of the Worm.
The law is thus universal. The second and third class of every circle traverse after birth the classes, to whose series they belong.
It would even appear that the classes, also of a lower circle, are subject to similar changes; at least many Entozoa, and thus the first class of the third circle, appearto undergo such a metamorphosis, since they first of all resemble an Infusory animal, next change as pupæ into Molluscs, and are then manifested for the first time as Worms.
3299. The Dermatozoa or Sensitive animals range in the following manner, according to the anatomical systems:
A.Intestinalanimals.B.Vascularanimals.C.Respiratoryanimals.1.Gastric animals.4.Venous animals.7.Reticular animals.Infusoria.Mussels.Worms.2.Intestinal animals.5.Arterial animals.8.Branchial animals.Polyps.Snails.Crustacea.3.Absorbent animals.6.Cardiac animals.9.Tracheal animals.Acalephæ.Kracken.Insects.
3300. According to the developments of the feeling-sense they stand thus:
A.Ovum-animals.B.Sexual animals.C.Cutaneous animals.1.Vitelline animals.4.Ovarial animals.7.Papillary animals.Infusoria.Mussels.Worms.2.Albuminose animals.5.Orchitic animals.8.Pedal animals.Polyps.Snails.Crustacea.3.Involucral animals.6.Renal animals.9.Alary animals.Acalephæ.Kracken.Flies.
3301. From these tables the number and kind of relationships or affinities is readily deduced. There is aRelationship of Proximity, as that between Infusoria, Polyps, and Acalephæ.
ARelationship of Repetition, as of Infusoria, Mussels, Worms. There is also aRelationship of Series, which takes its rise from the parallelism of the classes. The two last relationships have been confounded together under the termanalogy, which at best is but a word of random definition.
Second Province—Sarcozoa, Cephalozoa.
FOURTH CIRCLE—SARCOSE ANIMALS.
3302. The system of motion and sensation, which broke forth so forcibly in the tegument, now passes over into other forms, into the globular form of bone, the fibrous form of flesh or muscle, and the point-form of the nerves.
3303. The nervous system when liberated from the vegetative organs is, or consists of, the myelon (spinal chord) and the encephalon, i. e. brain.
3304. These animals are therefore Osseous, Muscular, and Encephalic animals, whereupon the senses are proportionately developed, and constitute the basis of the highest animal forms—Sarcozoa. The Dermatozoa areasarcoseorfleshlessanimals.
3305. With the sudden appearance of the animal systems all organs of the head, such as tongue, nose, ears, and eyes, are also developed; no asarcous animal has nostrils. Now these parts, especially the nostrils, as marking the terminal extremity of the vertebral column, make up the head—Cephalozoa, or Cephalic animals.
Class 10. Osteozoa, Glossozoa.
3306. The animals, in which the osseous system for the first time makes its appearance are, theFishes.
The Fish alone has more bones than any other animal. It has dorsal rays, which are wanting in all others.
3307. The animal systems are for the first time slightly separated from each other. Bone, muscle, and nerve are rather a gelatinous mass, which only bids fair for becoming something higher; on this account the bones are frequently but soft cartilages or tendons, the muscle composed of white fibres like those upon the intestine or vessels, the nerve thick, oleaginous, and soft in texture, while the brain is in its constituent parts hardly comparable with that of the Thricozoa.
3308. The muscles of Fishes are not yet perfect in character, since they are devoid of individualization and red colour, and their fibres run mostly parallel with each other without uniting into tendons. Their muscular body is a muscular wall.
3309. The Fishes, ranking upon the first stage of the Sarcozoa, repeat the same stage of the preceding circle, and thus the Infusoria, Mussels, and Worms; or the stomach, veins, and branchial rete or network; furthermore, the vitellus, ovary, and skin, which systems must in them accordingly predominate.
Pelvis.
3310. In Fishes the pelvic organs, sexual parts, and tail predominate. The tail, as being an appurtenance of the pelvis, is larger and stronger than in other animals. It mostly makes up the largest part of the body, and is, properly speaking, its only motor organ.
3311. The sexual parts have still the form of the intestine, and occupy the greatest part of the abdomen. The ovaria are two sacs, like two Infusoria, in whose parietes granules are developed; even the testes are only two such sacs or seminal vesicles wherein the "milt" is contained. Fishes may be termed anorchitic, or animals devoid of testes.
The ova are small, consisting of spawn or roe without shell, but they separate into albumen and vitellus.
3312. External sexual parts are not present. Everything usually opens into a cloaca, which is thus here a true pharyngeal cavity.
3313. With the perfected formation of the head, the animal, so to speak, undergoes a sudden and entire change, and the sexual parts are developed with all their accessory organs, such as the sexual lung. Kidneys are present and mostly an urinary cyst. The kidneys are indeed still so amorphous and soft, that they more resemble coagulated blood than an organ, yet meanwhile agree in this respect with the 'milt' and branchial substance.
Abdomen.
The abdomen is not simply confluent with the sexual body, but thrust by it completely forwards. The anus mostly lies in front of the middle of the body.
3314. The intestine separates for the first time distinctly into cephalic and sexual, or small and large, intestine.
3315. The vitelline canal is the cœcum. This is very distinct in the Sharks and Rays.
3316. In Birds therefore the vitelline canal is the cœcum also, and the two cœca, falsely so called, which are placed upon the side of the rectum cannot represent the cœcum coli, or else the Bird must have three of these blind appendages or sacs.
3317. The spleen here appears for the first time; while the pancreas divides into a number of cœcal appendages.
Thorax.
3318. The thorax of the Fish is reduced within very narrow limits; it is like the first thoracic formation, and is thus a Mussel's thorax. The branchiæ with their opercula are similarly formed to the branchial plates and shells of the Bivalve Mollusca. The thorax is therefore attached only externally to the body, and the Fish is to be viewed as a Mussel, from between whose shells a monstrous abdomen has grown out.
3319. But this Molluscan thorax is conjoined with animal systems, and has assumed their noble or elevated type of structure. Here therefore the osseous and sarcose system blend together, and the higher formation of the thorax emerges into view.
3320. For the first time an advance is made towards the formation of a trachea, namely, by the branchial framework or skeleton, which opens into the mouth, and corresponds therefore properly to the larynx. Fishes are therefore the first animals which breathe through the mouth. In all the preceding classes the air entered the body, or the water found access to the branchiæ, by other routes.
3321. They may be termed Mouth-breathing animals, for the first formation of the trachea extends no further than to its junction or communication with the mouth; since, for it to be continued into the head and open self-substantially as a nasal organ, constitutes a second step in advance, which cannot be ventured upon in an Abdominal animal. In Fishes everything relates to the abdomen, and this is expressed by the first union of thetrachea having taken place with the pharynx or the mouth.
3322. But, at the same time that the trachea is inserted within the mouth, it opens externally and in the lateral direction upon the body, thus letting the water escape from it posteriorly after a mussel-like or sexual fashion. Thus, the trachea is not yet closed inferiorly, nor hence also the thoracic cavity. Between the head and abdomen there are still openings—branchial foramina.
3323. The trachea is itself, however, a thorax upon a small scale, consisting as it does of rings, or as it were ribs. These arches are not yet united by muscles with each other, and the water flows out between them into the apparent thoracic cavity, from which it next escapes beneath the branchial operculum.
3324. These tracheal rings are the branchial arches. The branchial vessels are tracheal and by no means pulmonary vessels.
3325. Thus, upon taking a retrospective glance at the matter, we may fairly conclude that the branchiæ of the Dermatozoa are not equivalent to the lungs of the higher animals, but are only the antetypes of the bronchi, being thus cervical organs.
3326. The trachea is thus formed prior or antecedently to the lungs, but is still membranous and devoid of any continuous connexion between its rings.
3327. The lung is an organ extraneous or foreign to the trachea, and becomes only as if accidentally associated with it.
3328. But a Sarcozoon is not devoid of lungs nor of aerial respiration; for, being the totality of all lower animals, it consequently unites in itself the respiratory apparatus of the Branchial and Tracheal animals; thus gills and lungs.
3329. In the Fish the first lung appears, that is to say, if we designate or interpret the respiratory organ in Insects only as tracheæ, which do not open into the mouth.
3330. The Fish's lung is the air-or swim-cyst.
3331. The lung is still subordinate to the abdomen and intestine. It is therefore still separated from the trachea or the branchial arches.
3332. Fishes swallow the air and drive it into the pulmonic cyst, where it is analysed or decomposed.
3333. This lung, so soon as it stands opposite to and enters into conflict with a branchia, is what serves to direct or control the action of the heart. It is only when the swim-bladder is allowed to hold good as lung, that the circulation in Fishes admits of being understood. For otherwise venous blood must flow into the heart, from this into the branchiæ, from these directly into the aorta, and so to the different organs without again entering a cardiac cavity, a structure which occurs in no other class of animals, but rather in every instance its reverse. The first heart is arteriose, not venous in all animals, even in the Mussels and Snails and in the embryos. Now, the Fish is still such an embryo, and has only an arteriose heart.
3334. Thus, the following is the "modus operandi" of the parts in question; the swim-bladder is the lung, in which, seeing that it contains air, the blood is oxydized; this oxydized blood flows into the heart and renders itarteriosein character, despite the concomitant influx of venous blood into that organ. Upon this, the blood passes out of the heart through a true aorta, which is called the branchial artery. Instead then of this aorta giving off only some twigs as bronchial vessels to the gills, and next proceeding to pursue its course as a main trunk through the body and along the back, it passes wholly to the branchiæ, i. e. it entirely becomes a bronchial vessel, is slightly oxydized, and then returns upon itself to form the aorta, which should have taken its course directly from the heart.
Senses.
3335. In accordance with the thorax, the corium or true skin is developed. It is mucous in character and muco-secernent like the intestine, from its being constantly in the water. The whole skin is undermined by mucous canals and perforated by their excretory apertures. These foramina of the lateral line are arrested, and metamorphosed branchial foramina, which have only retained the evaporative function of respiration.
3336. The remnants of the tegument's annulation are the scales. They are desiccated air-branchiæ, alary opercula or elytra, and consequently indicate that feature of the Insect, which has continued to work its way into the class of Fishes.
3337. Like the skin, so are the limbs—tegumental members. What is flesh and bone upon them, has kept quite close to the body, and that only which is designed for splitting into digits projects, constituting tegumental digits with cartilages—fins. These fins are something better than the lateral papillæ of the Worms, are furnished at their base with joints, and are in number only four, but crippled or stunted in every possible way.
3338. The fin-rays do not correspond to the digits, but to the nails. They are fibrillated nails, like the wing-feathers of Birds.
3339. Lastly, the head possesses all the organs of sense which belong to a head, but they are still far removed from their perfect condition.
3340. As the nervous system is the first mass, from which the remaining ones have been set free, so also is the nervous sense the first after that of the tegument, which appears as a whole, and serves as a pattern for the subsequent senses. The eye is the sense which is first developed most perfectly, not directly as regards its own completeness, but when considered in reference to the others.
As the sense of feeling has been at once manifested in the vegetative animals as a peripheric nervous sense; so antithetically orvice versâit is in the higher animals the light-sense, as being the central nervose sense, which appears.
3341. Hitherto both these senses stood altogether alone with each other upon the stage of animal existence,in order, as it were, to play their parts in mutual consent; but so soon as the sense of feeling became individualized into tactile organs, then also the eye made its appearance in a detached or isolated manner.
3342. The Fish's eye is upon the whole composed of the same structures as in the Mammalia; but it is devoid of motion and external coverings.
3343. The ear, as being the sense of motion, has scarcely withdrawn itself from the brain, has not yet become a true external organ, and that portion of it which appears externally, is subservient to inferior systems, such as the branchiæ or gills.
3344. The external auditory organ has become confluent with the branchial aperture, and the auditory ossicles have become parts of the branchial operculum.
3345. In the internal ear only the three semicircular canals have been left. The cochlea is not yet developed.
As true palpebræ or eyelids are wanting to the visual organ, so also are the conchs of the external ear.
3346. The nostrils exist, because a vertebral canal, which terminates in them, is present; stoutly-developed olfactory nerves are also present, so that the sense of smell cannot be wanting. Only this sense has not yet taken the respiratory organ into communication with itself, and both therefore live for themselves in an arrested or stunted condition. This nasal organ does not open into the mouth, admits of neither water nor air passing through it, and therefore serves not as a test-organ to the respiratory process. This is my main point for distinction of Fishes from Reptiles.
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 appearsfor the first timein the animal kingdom as a perfect organ provided withmuscles, and a lingual bone, as in Man; Fishes are, as regards the development of this sense theGlossozoa, Lingual or Tongue-animals.
3350. As Fishes are the repetition of the intestine and vitellus, so they may be termedabdominalor ratherPelvic 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 theReptilia.
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-bladder 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-bladder 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, aReptile.
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 calledAbdominal 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 thetransitional 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 fœtus. The heart of Reptiles is therefore a persistent fœtal 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; theirureters usually unite into a large urinary cyst. Thus, the sexual lung is also significantly developed.
3372. Many of these urinary cysts split, as in the Tortoises, into two cornua. This is the form under which the bladder again occurs in Birds, where its two cornua have been incorrectly termed cœca, but the urinary bladder 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 cœcum, 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 andnaked; 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 areRhinozoa.
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 theBirds.
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.