endowed with muscular motion, the foetal water is also absorbed.
Nutrition is therefore in the commencement an absorption carried on by
the integument, and lastly by the intestine.
2. _Respiration._
3018. The respiratory organ of the foetus is the chorion, and in
particular the placenta. Its tissue is like that of the branchiæ or
spleen.
3019. The arterial blood transmitted through the umbilical vein is
conducted through the foramen ovale into the left ventricle of the
heart, and from thence directly to the principal organ of the foetus,
the brain and spinal cord. From hence it returns, venous in quality,
to the right side of the heart, and from thence through the ductus
arteriosus into the inferior or descending aorta, from which, pursuing
its course through the umbilical arteries, it again reaches the
placenta, in which it undergoes a renewed oxydation.
3020. If therefore the umbilical cord be compressed, the foetus
dies suddenly, as happens indeed accidentally in certain cases, which
completely resemble those of death produced by suffocation. The chick
when in the egg dies, if the egg-shell be coated over with varnish, or
if the egg be submitted to the noxious influence of gases which are
devoid of oxygen.
3021. The respiration effected through means of the placenta, admits
also of being proved by the sudden change which occurs in the
circulation after birth. No arterial blood being then any longer
brought to the heart through the umbilical vein, the left heart is
no longer stimulated, and the foramen ovale collapses and is closed.
Thus, all the blood enters the right side of the heart, and finding no
thoroughfare into the ductus arteriosus, it is driven forcibly into the
lungs, which now expand, and thereby leave an empty space between the
pulmonary vessels, into which the air rushes in.
3022. The first act of respiration is therefore the result of the
lungs being injected with venous blood, and thus of necessity ensues.
When, on the contrary, cases arise causing pulmonary suffocation, the
blood then regurgitates to the umbilical vessels, in order to reach the
original branchia or placenta.
3023. Another process of respiration is found to take place in the
vessels of the allantois. Its fluid becomes oxydized and penetrates
through the urinary cyst into what have been called primordial
kidneys. This kind of respiration through the anus is persistent in
many Worms and larvæ of Insects.
3024. Finally, there is a respiratory process on the body of the embryo
itself through the branchial apertures on its neck; these in the Frogs
and Salamanders still continue visible after their exclusion from the
egg. This oxygen must be derived from the foetal water.
3025. Without doubt also the vitelline vessels respire, and thus each
vegetative system has its own process of respiration. The intestine
respires through the vitelline vessels, the vascular system through
the vessels of the chorion, the sexual system through those of the
allantois, the integument through the branchial apertures. The lungs
belong to, and perform respiration for the whole body.
_Decay of the Developmental Organs._
3026. When all the organs are developed, the intestines are drawn
together with the vitellus into the abdomen. The chick is still
nourished several days after exclusion from the egg by the vitelline
mass, which passes through the vitelline canal into the intestine. The
vitelline membrane subsequently becomes flaccid, and finally disappears
through maceration. In the Mammalia the umbilical vesicle separates
at an earlier period from the intestine, and continues to lie in the
umbilical cord.
3027. The secernent point of the vitelline membrane or of the umbilical
vesicle is the coecum.
3028. There are therefore two intestinal systems, which branch off in
a bifurcated manner from the coecum, namely, the sexual intestine and
the small or truncal intestine.
3029. All embryos have originally umbilical herniæ, which do not
originate through protrusion of the intestines out of the abdominal
cavity, but through their entrance into the latter being retarded.
3030. The umbilical herniæ therefore indicate an earlier condition of
the animal, which has originated through arrest of the development.
3031. At birth all the enveloping membranes die, and their point of
liberation is called the navel or umbilicus.
3032. The animal has originated through the umbilicus, and through this
has it respired.
3033. All animals which breathe by the anus, do so properly through the
navel; animals of this kind are fundamentally umbilical animals.
_Parallelism of the Foetus with the Animal Classes._
3034. During its development the animal passes through all stages of
the animal kingdom. The foetus is a representation of all animal
classes in time.
3035. At first it is a simple vesicle, stomach, or vitellus, as in the
Infusoria.
3036. Then the vesicle is doubled through the albumen and shell, and
obtains an intestine, as in the Corals.
3037. It obtains a vascular system in the vitelline vessels, or
absorbents, like as in the Acalephæ.
3038. With the blood-system, liver, and ovarium, the embryo enters the
class of bivalved Mollusca.
3039. With the muscular heart, the testicle, and the penis, into the
class of Snails.
3040. With the venous and arteriose hearts, and the urinary apparatus,
into the class of Cephalopods or Cuttle-fish.
3041. With the absorption of the integument, into the class of Worms.
3042. With the formation of branchial fissures, into the class
Crustacea.
3043. With the germination or budding forth of limbs, into the class of
Insects.
3044. With the appearance of the osseous system, into the class of
Fishes.
3045. With the evolution of muscles, into the class of Reptiles.
3046. With the ingress of respiration through the lungs, into the class
of Birds. The foetus, when born, is actually like them, edentulous.
3047. After birth it is suckled or fed. The milk is the nutrition
continued by means of albumen; for the mammæ are verily only the
albuminous vessels of the Bird, which are placed free and external in
the Mammiferous animal. After the time for sucking is past the young
one obtains teeth; and thereby becomes for the first time independent
of the mother, and passes over into the class Mammalia. Now, should
the sketch here afforded of these parallels be not in all respects
correct or justifiable, still sufficient proof remains, that a perfect
parallelism is found to take place between the development of the
foetus and that of the animal kingdom.
3048. Animals are only the persistent foetal stages or conditions of
man.
3049. Malformations are only persistent foetal conditions, or animal
formations in individual animal bodies.
3050. Diseases are vital processes in animals. Pathology is the
physiology of the animal kingdom. A human foetus is a whole animal
kingdom. (Vid. Oken's 'Die Zeugung,' 'Beyträge zur vergl. Anatomie,'
and 'Ueber die Nabelbrüche.')
_Periods of Life._
3051. If the young in the ovum or in the mother's body resembles the
aquatic animals, and has passed through their organization; so after
birth does it belong to the air-breathing animals and traverse their
organization.
3052. One period is that of sucking; the edentulous condition of the
Bird. This is called the suckling age, baby-hood or infancy.
3053. One is that of the eruption and persistence of the milk-teeth;
the condition of the Rodentia, a repetition of the gelatinous animals.
This is the age of childhood.
3054. One is the eruption of the permanent set of teeth until the
attainment of puberty, or the development of the sexual functions;
the condition of the Marsupialia; repetition of the Conchozoa or
Shell-animals. This is boyhood.
3055. From the state of puberty until the development of the faculty of
understanding; the condition of the Shrews and Bats, the repetition of
Insects. The age of youth.
3056. The period of the understanding passes through the Ungulata, and
is a repetition of Fishes, Reptiles, and Birds. This is the first stage
of manhood.
3057. After the understanding the reason matures; this is the condition
of the higher Mammalia up to Man; it is a repetition of the Mammalia.
This is adult age or mature manhood.
3058. Then follows the decadence or dying off of the sexual functions;
a retrogression through the animal classes. Gray old age.
3059. Finally, the reason and understanding die; childhood returns and
terminates with the death of the vegetable in the animal.
3060. Death results through the sexual animal.
3061. Death is only a continuous growth through retrogression into the
organic primary matter or Infusoria.
3062. Death is an organized decomposition.
3063. Decomposition is a forming of seeds, ova, and foetuses.
3064. Dying is a multiplication of self.
III. ZOOLOGY.
3065. Zoology is Zoogeny divided and self-substantially represented.
What in Zoogeny was the organ of a single indivisible animal here
becomes the organ of a separated animal, or becomes a self-substantial
animal.
3066. The self-substantial animals are only parts of the Great animal,
which is the Animal Kingdom.
3067. The animal kingdom is only _one_ animal, i. e. the representation
of animality with all its organs, each of which is a whole for itself.
3068. A single animal originates, if a single organ frees itself
from the general animal body, and yet exercises the essential animal
functions.
3069. The animal kingdom is only a dismemberment of the highest animal,
i. e. of _Man_.
3070. Animals become nobler in rank, the greater the number of organs
which are collectively liberated or severed from the Grand animal,
and which enter into combination. An animal, which e. g. lived only
as intestine, would be, doubtless, inferior to one which with the
intestine were to combine a skin; and that animal again must be
regarded as higher than the latter, which should present, in addition
to these organs, vessels, liver, branchiæ, tracheæ, and lastly bones,
&c.
3071. Animals are gradually perfected, entirely like the single animal
body, by adding organ unto organ. The animal kingdom is developed
through the multiplication of the organs.
3072. Each animal ranks therefore above the other; two of them never
stand upon an equal plane or level. Animals are distinguished by their
position of stages or degrees from each other, by the number of their
_different_ organs, but not by the division of a single organ.
3073. The animal system cannot be arbitrarily disposed according to
this or that organ, just as it may chance to meet the eye; but only in
accordance with the rigid prescripts of the animal body's genesis.
3074. The animal body separates into two series of organs, which,
corresponding with, pursue a proximal course in relation to, each
other; into the Anatomical systems and the Sensorial organs, unto which
the sexual parts appertain.
3075. The number of the sensorial organs is 5, and they thus stand
according to their genetic development one above the other:
Tactile sense or Skin.
Gustatory sense or Tongue.
Olfactory sense or Nose.
Auditory sense or Ear.
Optical sense or Eye.
3076. In animals, which are characterized by the sense of feeling or
touch, the other sensorial organs must be either still wanting, or if
present but imperfectly conditioned, i. e. not constituted like those
of man, who is the type, pattern, or paragon for every formation.
3077. Their sensations are limited to those of general touch or
feeling, and of those derived through the medium of the other senses we
meet with but feeble manifestations.
3078. Their body itself will only be a tegumentary body, with the
organs subordinated to the integument, namely, the _viscera_. They
are therefore devoid of a true tongue, of a nose, and of ears and
eyes consummated after the fashion of these organs in man; they are
devoid of an osseous, muscular, and myelonal (spinal chord) system, and
therefore of the nose "in toto," as being the anterior extremity of the
myelon.
3079. Such are what have been called the Invertebrate animals, which
are consequently, in accordance with their physiological signification,
Splanchnic or _Tegumentary animals_.
3080. The tongue exhibits for the first time in Fishes a resemblance
to the human structure, while their nose, ears, and eyes have not yet
attained the latter grade of perfection. To the nose are wanting the
posterior nasal foramina, to the ears the external auditory meatus, to
the eyes the palpebræ and power of motion.
3081. In the Reptiles the nose opens for the first time into the mouth,
and serves for the thorough passage of air. It is thus developed as in
Man, while to the ears the external auditory meatus and cochlea are
wanting, the eyes being barely endowed with lids and motion.
3082. In Birds, for the first time, the external auditory meatus, as
well as the cochlea, is exhibited in its perfection, while the eyes are
scarcely gifted with motion, and have only the inferior lid perfect;
the tongue and nose, with the limbs also, have again become retrograde
in character.
3083. For the first time, in the Mammalia, the eyes are moveable and
covered with two perfect lids, without the other organs of sense having
suffered degradation through this completion of the eyes.
3084. Thus in respect to the Senses there are only 5 animal divisions
of equal value or worth. They should properly be called classes; but,
as the lowest division, from comprising within itself the viscera or
the vegetative systems, is very rich in contents; were we to call these
divisions classes, many inequalities in rank, and hence also in the
number of the orders and families, would originate--
1. Dermatozoa _Invertebrata._
2. Glossozoa _Pisces._
3. Rhinozoa _Reptilia._
4. Otozoa _Aves._
5. Ophthalmozoa _Mammalia._
3085. Now, with the sense of feeling, or the integument, the sexual
system is associated or conjoined, and that indeed as the first or
lowest development of the tegumentary system. Nevertheless, the
sexual system divides into two groups, into the sexual organs, which
are impressed with a true sensorial signification, and into their
product, or the sexual juices, and the ovum or foetus. With these two
divisions the development of the integument proceeds "pari passu."
In the ovum the tegument and its contents are not as yet separated.
Both consist of a transparent mucous or gelatinous mass, as is
exemplified by the vitellus and albumen; such is the case also in the
Infusoria, Polyps, and Acalephæ or Sea-nettles.
In the sexual organs, however, both parts separate into membranous
capsules or cysts, and glandular contents, as in the roe or ovary; milt
or testes; kidneys, with furthermore the oviduct, penis, and urinary
cyst. The latter are sentient membranes. Such is the case in the
Bivalve Mollusca, and Snails.
In the next place the tegument becomes, for the first time, a
self-substantial organ of sensation by appearing as an envelope of the
body; the vesical form is then repeated, and by this means the annular
character originates as a series of cysts arranged one behind the
other; it is thus a veritable skin, from which, finally, the members
sprout forth, as in Worms and Insects.
The Dermatozoa will accordingly range in three stages.
1. Blasto- or Oozoa.
2. Sexual animals.
3. Cutaneous "
An annulated tegument, cutis or true skin, appears for the first time
in the _Worms_, with here and there lateral filaments and tentacula.
True feet and antennæ appear in the _Crustacea_ or _Crabs_. Lastly,
feet and wings in the _Insecta_ or _Flies_.
3086. The external sexual parts, especially the male, first make their
appearance, and that indeed with a very striking amount of development,
in the Snails, and in like manner the body of the Bivalve Mollusca
or Mussels has become almost a complete mass of ova or roe. In the
Cuttle-fishes the first traces or rudiments of urinary organs appear.
The animals which belong to this group are accordingly the _Conchozoa_
or Shell-animals.
3087. Animals, which are directly resolvable into sexual fluids,
or that represent parts of the ovum, are the gelatinous Infusoria,
Polyps, and Acalephæ. Unto this category belong the _Protozoa_ or
_Mucus-animals_.
3088. The complete subdivision of animals, according to the organs of
sense, would consequently stand thus:
I. Dermatozoa Invertebrata.
1. Oozoa _Protozoa._
2. Glandular animals _Conchozoa._
3. Cutaneous " _Ancyliozoa._
II. Glossozoa _Pisces._
III. Rhinozoa _Reptilia._
IV. Otozoa _Aves._
V. Ophthalmozoa _Thricozoa._
3089. Unto these organs of sense the anatomical, or internal parts,
are subordinated, and range parallel to them in a striking manner. The
following is their order of succession in accordance with that of their
origin:
1. Intestinal system.
2. Vascular "
3. Respiratory "
4. Osseous "
5. Muscular "
6. Nervous "
3090. That the vegetative systems are correctly arranged after this
manner, is proved chiefly by their order of development in the animal
series.
3091. The animals, occupying the lowest grade, are nothing but an
intestine, which is in many instances scarcely separated or distinct
from the tegument; they are devoid of vessels and branchiæ, and are
barely provided with self-substantial ovisacs. Their body consists
of one or two concentric cysts of an homogeneous and transparent
substance--_Intestinal animals, Protozoa_.
3092. When the intestine is freed from the mass of the body, both then
obtain the form and substance of tegumental cysts, whereof the external
being only an intestinal tunic, thus represents the peritoneum. They
are now, however, united by means of a vascular system, which is again
surrounded by a cyst, and thus by a pleura. Their body consists of
three concentric cysts; intestine, peritoneum, and pleura. It contains
too a liver and self-substantial sexual parts--_Vascular animals,
Conchozoa_.
If these cysts be repeated in the direction of the axis, the tegument
becomes an annulated skin. An annulose animal is a multiplied cystic
animal. Associated with this character, the respiratory organs
are gradually evolved to form vascular plexuses, branchiæ, feet,
tracheæ, and wings, while the sexual parts are for the most part
separated--_Ancyliozoa, Respiratory animals_.
3093. The osseous system first appears in the Fishes, along with
imperfect, mostly tendonless, and only white muscles, as also a
myelon that is only developed into a stunted encephalon, in which the
brain-organs of the Thricozoon are in great part wanting.
3094. Typical, or true muscles, provided with tendons, and of a red
colour, are first exhibited in the Reptilia.
3095. A complete nervous system, pretty similar to that of the
Thricozoa or Pilose animals, having a cerebrum and cerebellum, with
similarly distributed and delicate nerves, is first displayed in Birds.
3096. According to the anatomical systems there are, therefore, six
divisions of animals:
A. Splanchnozoa.
1. Intestinal animals _Protozoa._
2. Vascular " _Conchozoa._
3. Respiratory " _Ancyliozoa._
B. Sarcozoa.
4. Osseous animals _Pisces._
5. Muscular " _Reptilia._
6. Nervose " _Aves._
3097. The Pilose animals first originate through completion and
combination of all the organs of sense. They are _Æsthetic_ or
_Sensorial_ animals.
3098. The arrangement of animals, according to the organs of sense,
coincides consequently with that derived from the anatomical systems,
and each animal division is therefore determined by two principal
organs, by a vegetative and an animal. Every animal is at once a
vegetable and animal body, the inferior kinds being partly so, but the
highest or the Pilose animals entirely so, or in every respect, i. e.
in them are found all the anatomical systems, and all the sexual and
sensorial organs.
3099. The signification of animals is accordingly as follows:
I. _Anatomical Systems._
A. _Vegetative Systems._
1. Intestinal animals.
2. Vascular "
3. Respiratory "
B. _Animal Systems._
4. Osseous animals.
5. Muscular "
6. Nervose "
7. Sensorial "
II. _Organs of Sense._
A. _Tegumental Sense._
1. Oozoa _Protozoa._
2. Glandular animals _Conchozoa._
3. Cutaneous " _Ancyliozoa._
B. _Cephalic Senses._
4. Glossozoa _Pisces._
5. Rhinozoa _Reptilia._
6. Otozoa _Aves._
7. Ophthalmozoa _Thricozoa._
The ovum divides into vitellus, and albumen, along with the calcareous
shell, and into germ or envelopes; the intestine into pharynx or
stomach, bowels and absorbent vessels, thus:
1. Gastric animals Vitelline animals _Infusoria._
2. Intestinal " Albuminous " _Polyps._
3. Absorbent " Involucral " _Acalephæ._
The sexual parts divide into female, male, and urinary organs; the
vessels into veins, arteries, and hearts, thus:
1. Ovarial animals Venous animals _Mussels._
2. Orchitic " Arterial " _Snails_.
3. Renal " Cardiac " _Kracken._
The annulated tegument divides into papillæ, feet, and wings; the
respiratory organs into tegumental network or rete, into branchiæ and
tracheæ, thus:
1. Papillary animals Reticular animals _Worms._
2. Pedal " Branchial " _Crabs._
3. Alary " Tracheal " _Flies._
When parallelized with the organs of plants, the following remarkable
relationships between them are rendered apparent:
1. Cells | Stomach | Vitellus _Infusoria._
2. Bark | Intestine | Albumen _Polyps._
3. Root | Absorbents | Envelopes _Acalephæ._
4. Ducts | Veins | Ovary _Mussels._
5. Liber | Arteries | Testes _Snails._
6. Stalk | Hearts | Kidneys _Kracken._
7. Tracheæ | Retia | Papillæ _Worms._
8. Wood | Branchiæ | Feet _Crabs._
9. Foliage | Lungs | Wings _Flies._
10. Seeds | Bones | Tongue _Fishes._
11. Pistil | Muscles | Nose _Reptiles._
12. Corolla | Nerves | Ears _Birds._
13. Fruit | Senses | Eyes _Thricozoa._
A. DIVISION INTO PROVINCES.
3100. The animal body divides first of all into the vegetative and
animal. There will therefore be animals in which the former, and others
in which the latter, systems predominate. The kingdom consequently
separates into a vegetative and into an animal province. The vegetative
parts are all tegumental developments, and thus the creatures in whom
they prevail are _Splanchnic_ or _Visceral animals_, but the animal
parts are developments of the flesh, and constitute the _Sarcose
animals_.
_First Province. Splanchnozoa._
3101. Unto the Splanchnic or Tegumental animals are wanting bones,
muscles with the nerves belonging to them, and thus the neural axis or
encephalon; they are consequently devoid of bone, muscle, and brain,
being in a word _asarcose_ or _fleshless_ animals.
The tegument is, however, the general organ of sensation or feeling;
they are thus _Sensitive animals_.
3102. In them, developments only of the sense of feeling can occur,
such as sensitive papillæ, tentacula, feet, and wings. All the
remaining organs of sense can only be exhibited as rudiments of a very
feeble or stunted character. They do not possess a true tongue, nose,
ears, and eyes, i. e. constructed after the type of these organs in
Man. The eyes only, from their being the sense of the animal system
proper, can assume a definite kind of development.
3103. But, these organs of sense are the sensorial organs of the head,
or rather are the head itself; the Tegumental animals are therefore
devoid of a true head. They only possess such an one, in so far as it
is determined by the tegument and nervous sense, by the mouth and the
eyes.
These animals are what have been called _Invertebrata_, a name which
is, however, defective, from its indicating the absence of one part
only or of a single animal system, while the word _flesh_ comprehends
bones, muscles, and nervous mass; they are _asarcose animals_. But
even this last appellation is not correct, because it is negative.
Their positive system, or that under which they actually exist, is the
tegument; so that the name of Dermatozoa or Sensitive animals, is the
only proper one.
As the tegument includes the viscera and forms therefore the trunk
alone, they may thus also be designated _Trunk-animals_.
_Second Province. Sarcozoa._
3104. As in the animal body, bones, muscles, and encephalic system are
suddenly associated with the tegumental system; so also does a second
series of animals, having these systems, suddenly originate. Now, as
the first formation of the osseous system is the vertebra, so all these
animals have, as is generally understood, a vertebral column, and are
on that account indeed Vertebrata; but, they are much more than this,
and hence the title is of too limited a character. Besides there are
among them animals, in which only the chorda dorsalis is present,
without the ring of the vertebral body being formed around it.
Along with the animal systems the head is for the first time developed
with its organs of sense--_Cephalic animals_.
These animals have consequently, in addition to the general sense of
feeling, a true tongue, nose, ears, and eyes--_Cephalæsthetic animals_.
B. ANIMAL CIRCLES.
3105. Animal Circles are representations of entire anatomical systems
as self-substantial bodies.
3106. Now, the vegetative body divides into three principal systems,
into the Intestinal, Vascular, and Respiratory system, with their
functions, or the digestive, nutritive, and respiratory processes.
There are therefore Intestinal, Vascular, and Respiratory animals.
_Circle I. Intestinal Animals._
3107. The intestinal system is the first form of body, or that from
which the other systems have not yet separated. The body of these
animals consists therefore of the homogeneous primary mass--the animal
protoplasma, mucus or slime--_Mucus-animals_.
Now, the protoplasma is a hollow globule. The intestinal system is
therefore nothing else than the original cystic form. Thus, there are
_Cystic animals_ like the Infusoria.
Again, cysts can increase in no other way, than by dividing into
their like, or engendering cysts within themselves. The first kind of
increase or multiplication of species is thus fissiparous, or produced
by division.
The newly-engendered cysts are to be compared with the vitellus, and
when they have attained perfection, to the ovum. They are therefore
Oozoa or _Ovum-animals_.
In these animals consequently there are no separated sexual parts,
namely, in addition to the vitelli, neither testes nor renal organs,
or at least only obscure indications of them. In these Cystic animals
the lowest feeling only, that of the _sex_ or _general sensation_, can
occur.
The Oozoa or Cystic animals, when compared with the plants, are the
first flower that has been set free, or in other words, a flower which
no longer stands polarwise upon a stem, because it is not developed in
the differencing air, but in the indifferent water. It may be said that
nature, having brought matters as far as the development of the sexual
parts, then quits or passes out of the vegetable world; while these
parts, or even the entire plant, requiring now no longer the stem and
root, become a root themselves, and in behalf of this enter the water.
Animals, which have the form of flowers, are round or radiiform. There
are _Radiata_ or Radiated animals.
3108. These _Anthoidal_ or Flower-like animals are Infusoria, Polyps,
Acalephæ; being single or double concentric cysts.
3109. We may regard the Flower-animals as the fundamental mass of
the sexual parts, which has attained unto free motion. They are sex
throughout, or nothing but sex; it cannot therefore be said that they
possess sexual parts like the plants, but that they are sexual parts.
They are sexual parts that swim.
3110. Formerly, most of these Anthoidal animals were actually taken
for real plants, on account of their floral and ramular form, and even
their very substance; so slightly withdrawn are they from the vegetable
kingdom. The whole difference between the two is effected by the water.
Could we transpose them into the air, they would then become real
plants.
3111. Now, as the vegetable flower is not a mere sexual system, but
is also stock or trunk; so also is the animal flower at once an organ
of digestion, respiration, and nutrition. The lowest condition of
these organs is, however, only one of absorption, evaporation, and
rigidification; these processes will therefore be present also, though
only upon the lower stage--they are Intestinal animals; for in a simple
intestine the same processes could occur, only within each other,
whereas they are mutually dissevered or set apart in intestine, lung,
and capillary system or parenchyma.
3112. The sexual parts are themselves viscera, or the viscera
themselves are sexual parts, just as the fungus is at one and the
same time root and seed-capsule. The sexual parts themselves absorb,
respire, and nourish.
The floral sac is not therefore a mere sexual sac, but also an
absorbent sac; upon a somewhat higher grade it is even a digestive sac,
the sac-wall itself being a respiratory and nutritive paries or wall.
The sexual function has at once become an ingestive function, tending
unto nutrition, or the deglutition of the food is itself an act of
copulation.
The sexual capsule in these animal flowers can as well be termed
stomach as uterus, and its wall ovary as well as branchia.
3113. As being of a sentient, mucous nature, they are point-substance
or nervous mass. The tentacula are higher organized stamina, and thus
occur as cilia, surrounding the oral aperture or mouth, as in the
Infusoria. These palpi or feelers are, from being organs of ingestion,
both male penes as well as digits or tongues, as in the Polyps. Their
structure is still wholly tubular, while their elongation appears
to be for the most part effected by injection with water--they
are absorbents, as in the Acalephæ. The Oozoon brings forth young
in the same cavity, in which it digests and by which it respires,
and impregnates itself with the same filaments, whereby it seizes,
swallows, and tastes its food.
In the bottom of the cavity of the Germ-animals, granules develop,
which are born or escape through the floral opening--pharynx, and
again become similar beings. In others the granules also sprout forth
attached to the walls of the cavity, remain there some time united
with the parent animal, and thus completely represent the mode of
propagation in plants by means of gemmules or buds. Among the Polyps
and Acalephæ it is well known that the ova issue from apertures near
the mouth; while in the Actiniæ this is stated to take place from the
stomach. The ovaria are, as is well known, situated between the stomach
and parietes of the body.
3114. The intestinal animals are an entire animal organism, but only in
the chaotic condition. They are the fundamental tissue, the cellular
system of the animal, and the higher animals are only separated cells.
3115. The propagation is in every respect similar to that of plants.
Now, as the seeds are the whole plant upon a small scale, so is the
granule or ovum the entire animal; it is liberated through the pharynx
and continues to grow merely by increasing in size. But if the young
animal protrude through the tegument, that is a true gemmiparous
propagation.
3116. Those Oozoa, which like plants can develop buds, consist of
several animals, and may be cut in pieces like plants; when each piece
becomes again an entire animal.
3117. The Oozoa represent those products of nature which are prior
or antecedent to the animal world; namely, first of all plants, and
further still the inorganic kingdom also, or the earth, since they have
originated in the water and can be as well developed from the stones
as the Lichens. There are therefore Lithozoa or Stone-animals, and
Phytozoa or Plant-animals, among the Oozoa.
3118. Would we compare these animals with the parts in plants, they
then represent their cell-development, or cells, bark and root. They
are themselves either vesicles, as the Infusoria, or barks, as the
Corallines, or a root-like fascicle of tubes, as the Acalephæ.
3119. In the animals, however, the cells have become stomach, the bark
intestine, the root absorbents. The Oozoa represent therefore the
aggregate of the intestinal system, the primary mass of the animal body.
Their whole body is a digestive body, or parenchyma, traversed in many
species in all directions by tubes or absorbents, as in the Acalephæ.
As yet no nervous filament, nor any muscular fibre, &c. has been
separated from their mass, as in like manner a tegument has barely been
freed or separated from the intestine. These animals are nerveless and
sine-tegumental, precisely because they are wholly made up of nervous
mass and tegument.
_Circle II. Vascular Animals._
3120. In the next place the digestive separates completely from the
tegumental function, and each constitutes a function for itself, but
which now being separated from its fellow could no longer subsist.
Between the two therefore is formed the nutritive function in the
_vascular system_.
Now, the vascular system of the self-substantial intestine is the
liver. This organ will therefore for the first time make its appearance
in this animal circle--_Hepatic animals_. Upon a higher stage, salivary
glands are also developed on the intestine, and will here likewise
begin for the first time to appear--_Salivary animals, Snails_.
3121. Through the separation of the viscera from the remaining
substance, this must necessarily remain behind as a hollow cyst or
tegument investing the former. The true free tegumental formation is
therefore by no means accidental, but is necessarily bestowed with
the viscera in the course of animal development. This tegument is
_peritoneum_. There are animals which are invariably bicystic, but
consisting of concentric cysts--_abdomens_.
Around the ventral integument, however, the vascular system also forms
its tunic; this is the branchial membrane or operculum--_pleura_,
mantle. There are tri-cystic animals--intestine, abdomen, and thorax
disposed concentrically around each other--Mussels. Their body is
therefore not articulated, but its parts are still inserted within each
other.
The Vascular animals are consequently multiplied Protozoa; or
Mucus-animals of the second power--_Ovum_².
The sense of feeling ascends upon its second stage, when its organ,
having been freed from the mass of the body, surrounds the viscera
as a self-substantial tegument. The feeling is then no longer one of
a merely general character, but is a definite perception of external
objects, a passive power of feeling.
3122. True muscles could not as yet originate in this skin, and that
for obvious reasons, although fibres are present; for the former are to
be brought under the signification of arterial fibres.
3123. Cilia, when furnished with fibres by whose agency they are
rendered moveable and susceptible of inversion, are called _tentacula_,
which here occur under every variety of form.
3124. Would we compare the Vascular animals with the plants, they
must then represent their ducts, liber, and stalk. The heart is the
stalk, the arteries liber, the veins tubes or ducts. These animals have
assumed also upon the whole the cauline or cylindrical form--Cauline
animals.
3125. From their having obtained in addition to the intestine only
the vascular system, they are still governed by the water, and live
therefore for the greatest part in this element. They have the first
mode of respiration and thus an aqueo-respiratory process--possess
branchiæ but not tracheal tubes.
3126. The sexual parts, which in the Germ-animals were still coalesced
for the most part with the body, here become self-substantial through
the separation of the teguments, make their appearance as a repetition
of the digestive system under the condition of a free or separate
system, and are evolved into true ovaria and even male parts--_Sexual,
Glandular animals_.
3127. The first step towards the evolution of male parts is, however,
only half achieved. Only one testis originates, while the other remains
behind as ovarium--_Androgynous_ or _Bisexual animals_.
3128. These animals, which are characterized by the vascular system,
and by the first self-substantial or external sexual parts, which
indicate organs of sense, are the _Conchozoa_, such as the Mussels,
Snails, and Kracken.
_Circle III. Respiratory Animals._
3129. When once the intestinal and vascular system, through perfection
of their individual parts, such as the liver and branchia, and
through separation of the sexual parts, are completed; then the
individualization of the tegument steps into view, and it becomes an
independent _respiratory system_.
3130. Through the increased process of oxydation the tegument hardens
and is converted into _horn_. All induration, however, only takes place
in opposition to soft places. The tegument therefore separates into
hard and soft rings--_Annulate animals_.
3131. The annulate tegument is a tracheal tube wholly converted into
a body. To distinguish it from the general tegument it may be called
the cutis or _skin_--_Cutaneous animals_. The annular tegument may
be regarded as a series of cysts placed one behind the other. The
Annulate animals are therefore multiplied Malacozoa; Mucus-animals of
the third power--_Ovum_³.
The respiratory organs, being in their lowest condition, will not as
yet be freed from the tegument; the vessels simply form a network
or projecting filaments and lamellæ--_reticular branchiæ_; as in
the _Worms_. The tentacular organs, from being yet soft and thus
scarcely moveable, are still very imperfect. Upon the lowest stage
the tegument or _skin_ simply feels; in the next place papillæ, and
finally filaments, originate, especially about the mouth--_Cutaneous_,
_Papillary_ and _Filamentary animals_.
3132. If the tegument, as being the original branchial membrane, is
converted into horn; then the branchiæ cannot continue as retia, but
must elongate above the tegument into filaments, ramules or lamellæ.
With this, these elongated branchiæ separate into two organs, one part
of them becoming indurated in like manner with the general tegument,
and supporting the other as gill. Horny branchial filaments, which
contain vessels, nerves, and fibres, are called _feet--Pedal animals_.
3133. The limbs or members of these animals are simply hollow tegument,
hollow hair, and are therefore thoroughly different from the bones or
the animal system.
The tegument thus hardens around the soft parts and the viscera.
A horny coat of mail originates, and thus we have horny or mailed
animals, in opposition to the Malaco-or Conchozoa.
3134. Beneath the horn, however, there must still be soft skin, and
this becomes fibrous by the strong oxydation which it undergoes.
Fibrous fascicles are attached to the coat of mail and to the hollow
limbs, and are consequently within the tubes.
3135. These fibrous bundles are not flesh, but a fibre-drawn
_tegument_, so that there are also no true muscles. They must on that
account too be numberless.
3136. The articulations or joints are external not internal; they thus
consist of tegumental tubes, not of bones, abutting against each other,
and are not surrounded by flesh. Hence, like all the preceding groups
they also are devoid of flesh--asarcose animals like all the preceding
ones.
3137. In the branchiæ, however, it is only the cauline portions which
become horny, while their ramules continue to perform the respiratory
function. The branchiæ therefore are appended to the extremity or roots
of the feet; or rather these latter form the branchial arches.
Annulate animals, having true or hornified and likewise annulated feet,
are called Crustacea or _Crabs_.
Thus, in these animals the sense of feeling obtains special and
moveable organs; they are _Tactile animals_.
Tactile organs are prolongations of tegument moved by muscular fibres,
which in some degree adapt themselves by pressure unto the forms of
objects, or have the power of seizing and retaining them--such as feet,
antennæ, maxillæ, palpi.
3138. But if the tegument be entirely converted into horn, and the
respiratory vessels have in this way disappeared within it, then the
internal respiratory organs are formed by inversion of that part of the
tegument which is between the rings, and through these openings the air
penetrates to the internal parts--stigmata, tracheæ.
3139. The tracheæ can first of all originate when the respiratory
process has attained its highest development, or, in other words, when
the creature breathes air.
3140. Lastly, in the air-breathing Ancyliozoa even the external
branchial lamellæ harden and are converted into _wings_--_Pterozoa_,
_Insects_ or _Flies_.
The wings of Insects do not correspond to the wings of birds; they are
not feet, but pedal appendages or _branchiæ_, and thus are no new or
unknown organ.
_Circle IV. Sarcose Animals._
3141. The second animal province may be regarded as the fourth stage in
the self-substantial development of the anatomical systems, although,
properly speaking, it ranks as regards its value or worth upon a level
with the three former circles, and resolves itself directly into three
stages, which accord with its three systems. But since these stages
are at the same time also classes; they should, for uniformity's sake,
retain the latter name.
3142. The animal kingdom accordingly divides into _four_ great
districts or circles.
CIRCLE I. _Intestinal Animals_, Oozoa--Protozoa.
II. _Vascular_ " Sexual animals--Conchozoa.
III. _Respiratory_ " Cutaneous " --Ancyliozoa.
IV. _Sarcose_ " Cephalic " --Vertebrata.
C. ANIMAL CLASSES.
3143. The animal Classes may be designated as the self-substantial
representation of a stage in the development of an anatomical system
or of the inferior organ of sense, and in the Sarcose animals of these
systems themselves or of the cephalic senses.
3144. There are then as many classes as there are stages of development
or systems. Thus the intestinal system separates into pharynx or
stomach, intestine and absorbents.
3145. The vascular system into veins, arteries, and hearts.
3146. The respiratory system into branchial membrane or skin, into
branchiæ, and into lungs or tracheæ, i. e. air-tubes. Taken in a strict
sense, such divisions do not constitute classes, as has been already
remarked.
3147. It is only the animal systems, which do not divide into several
functions, but remaining upon a level with each other, are simply
repeated in the higher organs of sense.
_First Province. Splanchnozoa, Dermatozoa._
FIRST CIRCLE. INTESTINAL ANIMALS, OOZOA.
3148. The intestinal animals are nothing but depressed cysts. They rank
therefore upon the lowest stage of development, and consist of mucus or
granular nervous mass--_Protozoa, Gelatinose animals_.
3149. It is an established fact that, with animals as well as
plants, the first function consists in imbibition or absorption,
and the body must consequently be an absorbent cyst or a pharynx,
which nevertheless takes up the food in the same way that the
tegumental lymphatic vessels absorb. We can therefore style these
animals pharyngeal or gastric, although the name is not perfectly
correct--_Infusoria_. Then the intestine associates with the pharynx or
stomach, so that they are Intestinal animals--_Polyps_ or _Corals_.
Lastly the intestine sends out absorbents, and then the animal consists
of pharynx or stomach, intestine and absorbents; such may be termed an
Absorbent animal--_Acalephæ_.
The Intestinal animals therefore divide according to the developmental
stages into three Classes.
_Class 1. Gastric, Vitelline Animals._
3150. The lowest animals commence with the water, which has scarcely
become mucus; they are nothing but drops, vesicles, which swim about
independently--_Protozoa_ or _Primitive animals_.
3151. The Protozoa correspond to the vitellus or the male semen, which
is nothing but vitellus in a state of solution. They are the animal
semen of the planet, the animal dissolved. Animal generation cannot
take a deeper commencement or origin. The stone, which is decomposed
into carbon mixed with water, can become nothing less than a point.
They are the animal germinal powder. The fungus is a tissue of
vesicles, which dissolves directly into seeds--fungus-powder or dust.
Thus, they are ovaria or testes which have dissolved into seed, fluid
testes--_Vitelline, Seminal animals_.
3152. The vitellus or semen is point-or nerve-mass dissolved. The
Vitelline animals are sentient or nerve-points, which have combined all
other processes in this identical mass. The divided point-mass ranks,
however, in the signification of vesicular or cellular tissue. These
animals are nervose cells.
3153. Nerve-cells must originate in every water, because every water
is in a state of tension with the earth and the air; thus, dissolves
the former and absorbs the latter. The water itself is a digesting and
respiring mucus.
3154. The nerve-cells have an internal cavity, from the surface
becoming oxydized and consequently converting itself into a denser
layer, or into tegument. This, however, can only take place at the
expense of the internal mass, as being that alone which abuts against
the external parietes and becomes rigid.
3155. As the animal life is not simply a single act of rigidification,
but a repetition of the same, alternating with solution, so must the
Protozoon again replace the mucus-granules which have been disposed of
from its interior; it must eat.
3156. It is a matter of indifference for the philosophy, whether the
reception of food is effected by one or several mouths. There are
Acalephæ and even Intestinal worms (Entozoa), which absorb by several
mouths, almost like plants.
3157. But in the animal the mouth or mouths is or are definite organic
openings, not merely interspaces or pores as in the plants; for they
rank in the signification of the blossoms, or of composite parts.
3158. It can be therefore said that every animal hath a mouth or
mouths, and consequently a stomach or stomachs.
3159. Their motions consist in abbreviations or straitenings of the
cyst. Indications can scarcely be present of the secretions of higher
organs, such as the intestine, vessel, branchiæ, liver, and such like
parts.
3160. On the contrary, developments of the tegument and nerves may
occur, the former as cilia which serve also as organs of motion and as
branchiæ, the latter as ocular points or rudimental eyes; for both are
none other than nervose tegument. The mouth of these animals is still
passive, and subordinated to the water. It is surrounded only by cilia,
which by the vortices produced by their movements in the water, impel
or draw the latter into the mouth and with it the food. Such animals
are called _Infusoria_.
3161. As the Infusoria are the seed or vitellus itself, so also
are they the very ovum, and require no special sexual parts for
propagation. They absorb, and are so nourished, and if there is a
sufficient quantity of the mass to admit again of its division into
several points, they thus divide. A magnified Infusorial animalcule has
become, as it were, an ovarium or a testis, which then produces seed by
dissolving itself into the latter. They are a constant conflict of the
organ and its product, of the Solid and Fluid, a vitelline and orchitic
process.
_Class 2. Intestinal, Albuminous Animals._
3162. With the separation of the cyst into an internal and external
layer, or into intestine and tegument, the animal must necessarily
ascend a stage higher, since it now contains two systems different from
each other, and is consequently a double Infusorium.
3163. The form of the _Intestinal animals_ passes gradually from that
of the globe into the tube--Tubular animals.
3164. They are tubular nerves surrounded by a tegument.
The cilia also are perfected and lengthen into filaments, which no
longer perform simply vortical movements, but now actually seize and
convey the food self-substantially into the mouth. Such animals are
called _Polyps_. Their multiplication takes place no longer by division
or fissure, but by ova and shoots, or ramification.
The oviducts or egg-tubes lie between the intestine and tegument,
and open upon the margin of the mouth between the tentacula. In many
instances the ovisacs, or cysts, hang also freely from other parts of
the body, as in the Sertulariæ.
The sprouts or offshoots detach themselves from the parent and become
independent animals; but they frequently continue to stand as ramules
upon the maternal animal, though they nourish themselves independently
of the latter.
3165. If the process of oxydation be augmented, then, the tube's
external wall indurates, becomes coriaceous, and, lastly, ceratoid or
horn-like in texture. The nerve-tubes or the animal proper can now
swim no longer, since one kind only of motion is left it, namely, to
protrude itself out of, and then retract itself within, the tube. It
consequently falls to the ground, and while the external mucus hardens,
it clings to the former; such are the Sessile or fixed Polyps.
3166. Sessile Polyps having coriaceous or horny tubes are called
_Plant-animals_, Zoophyta, Phytozoa.
3167. The adherent, dried and dead external tegument of the Polyp is
called _stem_. Such a ramified stem completely resembles a plant.
3168. These woody or herbaceous stems are not rooted in the earth, but
have the power of adhering firmly to every substance, to stone, glass,
shells, and such like bodies. They do not therefore draw in nourishment
through any root.
3169. The ramification is often wholly plant-like in character,
resembling that of a shrub with separate ramules, which even assume too
the form of leaves, and the animal tubes that of flowers.
But frequently the ramules grow together also by their extremities,
giving rise to a trellis-work, the production of which in plants is
impossible. The soft animalcules, which come in contact, cleave unto
each other, and grow together like wounded parts in the Sarcose animals.
3170. Upon the surface of the ramules or the leaves are apertures, out
of which the mucous substance protrudes the radiated mouth. But these
mouths are frequently, especially in the Cystic corallines, of two
different modes of formation. The one kind are cysts without filaments,
and contain ova, which are developed and fall out. The others have
filaments, which move and do not produce ova. The former look like
seed-capsules, the latter like flowers with stamina, while the entire
trunk resembles a monoecious plant.
3171. With increased oxydation calcareous earth is deposited in
the external tegument or rind, and the stem is converted into
stone--_Lithozoa_, Lithophyta, _Corals_.
This calcareous earth contains the most general acid, or the carbonic,
and thus oxygen combined with the inorganic carbon, while the bones
contain phosphoric acid, oxydized gelatine.
3172. As the calcareous earth is, properly speaking, only a granular
deposit in the tegument, like it is in the cartilages of the higher
animals; so is it not to be regarded as a free worm-tube, but as the
body itself. Meanwhile it forms a tube open above, from which the mouth
of the animal projects.
3173. As the animal ramifies, so also do the stony tubes increase, and
there originates a phytoidal or plant-like stem, but one consisting of
a stony mass.
3174. Thus the Coral is the earth-animal, and indicates the globular or
osseous mass under its first grade of formation in the animal kingdom.
But there are also Polyps, whose stem only originates through saccular
inversion of the upper portion of the animal's body; yet this is only
distinct in the soft stems. In most of the species, where a separate
intestine is to be found, it is probably only the upper part of the
body which is so inverted. Meanwhile there are some, whose intestine
forms a circle by returning upon itself, and opens into an anus.
3175. If then the Infusoria are the vitellus or seed of the animal
kingdom; in like manner the Corals are its ova. The carbonate of lime
is the shell surrounding the albumen, while the animal or intestine is
the vitellus--_Albumen-animals_.
3176. Nature forms these living ova, when she takes vitellus and
albumen out of the sea-slime, invests them with a shell derived from
the earth, and hatches them, after they have been vivified by sun and
air.
_Class 3. Absorbent, Involucral Animals._
3177. Did the former animals remain in the condition of ova, from want
of a perfect vascular system; they are next developed, so soon as
vessels appear and form a vascular plexus, into foetal involucra or
envelopes. These animals are vitellus with the vascular membrane.
3178. The Absorbent animals are no longer simple vesicles, but large
cysts or capsules like the developmental envelopes of the foetus,
along with a choroid plexus--_Involucral, Foetal-animals_.
This choroid plexus does not, however, consist of arteries and veins;
but is only a ramification of the intestine, so that the vessels are of
a lacteal character--_Absorbent animals_.
3179. In these animals there is no longer any egg-shell, but everything
has been taken up into the galvanic circle; the shell has itself become
organic and life-imbued. Their substance is still mucous or albuminous;
they are still vitellus, though converted into a vascular tissue.
3180. They therefore cling firmly nowhere; but swim about freely, like
brain-masses converted into radiated cysts.
3181. Free Mucus-animals, traversed by vascular plexuses, are
_Acalephæ_.
3182. There are Acalephæ which are simply air-sacs, like the air-sacs
of ova, to which hang ramified vessels as absorbent tubes--Cystic,
Tubular Acalephæ.
Others represent hemispheres with numerous absorbent tubes, which
concur in the middle of the animal to form a kind of stomach, from
which again other tubes pass towards the border, in order to elongate
into tentacula. Thus the absorbent vessels have become motor and
sensitive organs.
Besides this, many have around the mouth four large lobes, which
must be viewed as the antetypes of the sentient lobes of the Bivalve
Mollusca.
Lastly, others have a true mouth, which leads to a similar gastric
cavity, out of which the same vessels emerge and ramify. Both kinds are
called Hutquallen or Acalephæ.
There are yet others having the same structure, but oviform, with
respiratory lamellæ upon the absorbent tubes, Rippenquallen or Beroes.
3183. An Acalephan is a brood-egg, which swims freely about without a
shell.
3184. The vessels are quaternary in their distribution, and form a
cross, like the involucral vessels of the chick.
3185. In these animals the ova first begin to be detached and
agglomerated together in definite situations so as to constitute
ovaria. The number here is also four.
They lie usually within four cavities surrounding the stomach, and into
these wide apertures situated near to the mouth lead; they are at the
same time regarded as respiratory cavities.
In other species vesicles, wherein seminal animalcules are developed,
occupy the same situation. Here therefore is recognised for the first
time a separated sex.
In the Röhrenquallen or Physaliæ the ovisacs mostly depend externally
in the form of bells.
Besides this we find in the Acalephæ all sorts of laminæ, which are
probably organs of respiration.
It is not known what is the meaning of the air-sacs and of what the air
consists.
Most of the species emit light like globes of fire, just as many
Infusoria do also. It is probably a phosphorescence given out by the
mucus when passing over into a state of decomposition.
Very many have also the stinging property of the nettle; but, whether
the cause of this is chemical or mechanical, is not yet exactly known.
SECOND CIRCLE. VASCULAR, SEXUAL ANIMALS.
3186. So far, or in the ascending scale up to the Acalephæ, the animal
is only viscus with an absorbent canal, which is at the same time a
canal of evacuation, without a distinct intestine being set apart for
that purpose; such is the general rule.
3187. After the Acalephæ the formation undergoes a change; the
distinction between the exterior and interior is prominently displayed,
and the internal wall becomes freed as a separate and perfect
intestine along with a mouth and anus; the external wall appears as
a free tegument. But, seeing that two concentric and separated cysts
could not subsist without combination by means of the nutritive system
or the vessels; a perfect vascular system is formed, divided into
veins, arteries, and hearts.
The tegument, wherein the vessels become self-substantial, is the
branchial membrane. There is therefore placed around the intestinal
body a vascular body also, or branchial membrane, which is consequently
pleura or mantle (pallium), as in the Mussels. The body of the
intestine consists of intestine and peritoneum; that of the vessels of
branchiæ and pleura or mantle.
These animals are hence bisystemic, being both Intestinal and Vascular
animals; but, since the vascular system is a new addition, it is thus
characteristic of the circle, and its members must be therefore called
_Vascular animals_. With the vascular system, however, all its further
developments have been bestowed; thus especially the complication of
the vessels with the intestinal ramifications or, in other words,
the liver--_Hepatic animals_. The salivary glands also are a similar
complication, and in this series therefore they make their appearance.
Lastly, the renal glands are such a kind of vascular organ, or branchiæ
of the sexual parts; they also begin to be astir in this series.
With the separation of the systems into separate teguments or
membranes, the sexual parts also separate. The ovarium becomes an
independent organ furnished with its own excretory ducts; the male
parts are individualized to form veritable testes furnished with
excretory ducts, or even with a penis. Still this is all effected only
by degrees, or as yet within the confines of this circle.
These animals divide according to the viscera into Venous, Arterial,
and Cardiac animals; according to the sexual parts, into Ovarial,
Orchitic, and Renal animals.
_Class 4. Venous, Ovarial Animals._
3188. With the protrusion into view of the vascular system, the veins
are chiefly developed along with their principal organ, the liver, as
being the bond of union between the circulation and the intestine.
3189. The animals, which first bring to bear in addition to the
intestine a liver, are the Bivalve Mollusca.
3190. With the veins arteries also originate, but with a preponderance
of venosity or the venous character. The blood is lymphatic, colourless.
3191. The cardinal venous organ or the liver evokes also into existence
a corresponding organ of respiration, namely, free branchiæ with the
tegumental form--branchial laminæ or leaves.
3192. In the middle between the branchial laminæ and the liver, the
heart is evolved; this organ comprising always a ventricle with an
auricle, but consisting of a venous, membranous tissue almost devoid of
fibres.
3193. The first heart is in other respects arteriose; it receives the
blood from the branchiæ and transmits it to the liver as well as to the
remaining parts of the body, from which it proceeds directly to the
branchiæ without entering any venous or right heart.
3194. In these animals, as is well known, four branchial leaves lie
externally on the belly, which includes the intestine with a large
liver, and hangs together with the branchiæ as a separate purse within
the mantle.
3195. In the Mussel a structure originates for the first time, which
can be compared with a thoracic or pectoral cavity. What covers the
branchiæ, must stand in the signification of the thorax or chest. The
pallium or mantle of the Mussels is pleura.
3196. Their shells are branchial opercula (as in the Fishes). They are
secretions from the mantle, and everywhere accompany the branchiæ.
3197. The locket or hinge of the shell-valves corresponds to the
rachis or spina dorsi, as is especially distinct in the Teredines or
"ship-worms."
The shells of Bivalve Mollusca are a calcareo-thoracic box, open in
front, inverted behind, and moveable like ribs.
3198. The two sphincter or occlusor muscles signify shoulder and haunch.
3199. These animals begin for the first time to exhibit bilaterality
or symmetry, because in them there is stirring the idea of the osseous
formation. From the branchiæ being situated symmetrically upon both
sides, the cardiac chambers are also symmetrical.
3200. The pectoral tunic (mantle) usually elongates at the anal
extremity into two tubes, respiratory tubes, through which the water is
drawn in and thrust out or expelled. Such is the case in the highest
Worms or Holothuriæ, only there the respiratory tube leads into the
body itself. A similar arrangement is found in the Echini. Many aquatic
larvæ from all kinds of Insects or out of different classes breathe
through anal tubes. All these animals consequently repeat the Mussels,
and this formation admits of being followed out up to Man, where it
is left as allantois and primordial kidneys. The thorax of the Mussel
thus opens by the anus. But, since the thorax is that which is here
preponderating and is nearly the whole animal, so does the anus open
into the posterior respiratory tube.
3201. The Mussel can be regarded as an animal consisting of three
cysts or sacs inclosed within each other, namely, of intestine, around
this the ventral pouch, and around this again the thoracic sac or
mantle. If, moreover, the shells be regarded as a cyst, the animal then
consists of four sacs. The heart and branchiæ lie within the thoracic
cavity; intestine, liver, and ovarium within the abdominal or ventral
cavity. The Mussel is thus a doubled Acalephan.
What is termed foot in the Bivalve Mollusca is nothing else than the
abdominal tegument dilated in front to form a muscular ridge.
3202. The Mussels are embryos, in whom the liver originates, and
whose chorion acquires a placenta. Then again, as the embryo is
nearly all liver, and hangs surrounded by a watery fluid within the
widely-expanded chorion and amnion, so does the abdominal pouch hang
within the pallial cavity, or in the wide, water-full chest.
3203. In the abdomen there is still only the ovarium, and that indeed
very large. There are properly two ovaria, each of which, according to
my observations (vid. Göttinger Gelehrte Anzeigen, 1806. Stück 148),
opens laterally under the shoulder-muscle and gives exit to the ova,
which then enter within or between the branchial fringes, in order to
be there developed.
3204. Here the respiratory organs are still at the same time a kind
of uterus. The ova may be oxydized therein, like the embryo is in the
uterus. These branchiæ are probably still to be compared with, or
designated as, sexual branchiæ.
3205. In the back of the shoulder these animals have a highly vascular
organ with two excretory passages, which open near to the orifices
of the oviducts. I formerly regarded it as a kidney, but, according
to more recent observations, it should be a testis. In the anterior
part of the foot there is frequently situated a gland which ejects
a gelatinoid moisture, which hardens into glutinous filaments--the
byssus or beard. It is probably a memento of the tentacula of the
Acalephæ. There is besides also an organ in the feet of many Bivalve
Mollusca, which occasionally squirts a watery juice out to a great
distance. I have occasionally found this organ in our Teichmuschel. Its
signification is probably the same as that of the preceding organ.
3206. The organization of the Bivalve Mollusc can be thus most
distinctly described; it is an abdomen, wherein is an intestine with
mouth and anus, a liver and a double ovarium; upon the sides of this
abdomen are situated the branchiæ in the form of four laminæ; around
the branchiæ and the abdomen is the pleura or mantle, which is always
open posteriorly.
3207. The mouth is placed directly at the anterior extremity of the
abdomen, is devoid of neck and head, as also salivary glands; it
is consequently not a true mouth, but only a pharyngeal aperture.
Thereupon, however, are situated four sensitive lobes, which are in
structure exactly like the branchiæ--cephalic or pharyngeal branchiæ.
They are the further formations of the four arms of the Acalephæ.
3208. The Mussel has a perfect splanchno-neural system with ganglia and
a pharyngeal ring, which probably corresponds to the nerves that sweep
around it.
3209. The Mussel has no other organ of sense than that of the passive
sense of feeling, the tegument. It cannot once move its sensitive lobes
voluntarily; it has no lips.
3210. The abdomen only elongates in most of them to form a moveable,
variously constructed foot or _keel_, which cannot, however, creep
but only push. The progression of the Bivalve Mollusca is backwards,
as in the Acalephæ. In the Snails the ventral surface first becomes a
creeping _sole_.
3211. The Mussels repeat the Infusoria; are Infusoria with a bivalve
calcareous testa or shell.
_Class 5. Arterial, Orchitic Animals._
3212. In the preceding class of Bivalve Mollusca, it is in truth the
abdominal viscera only, such as the intestine, liver and ovarium, which
have been perfected; and then the veins and arteries with a membranous
heart. The cephalic organs, eyes, maxillæ, salivary glands, and even
moveable lips with tentacula, are wanting, as well as the muscular
heart. Lastly, the arterial sexual system or a self-substantial testis
and the penis were absent.
Now, bivalve Mollusca, which have eyes, maxillæ, a muscular heart and a
ventral sole or foot, with salivary glands and a penis, are Gasteropoda
or _Snails_.
3213. The Snails possess salivary glands, a trace of the tongue and of
maxillæ, moveable lips and tentacula, with thus an approximation to the
head, unto which the eyes are rarely wanting--Salivary animals.
3214. With the development of the head or rather of its inferior
organs of sense, the antagonism makes its appearance also in the
ovarium. A half of the ovarium is converted into the testis.
The Snail is therefore a Mollusc, which is female upon one side, male
upon the other.
3215. The androgynous or bisexual animal is, as a general rule,
asymmetrical.
3216. The mantle also or the branchial cavity obeys this want of
symmetry. The branchiæ of one side dwindle down; those of the other
turn with the mantle towards the head, and the respiratory aperture
occurs upon the back.
3217. With the one-sided evolution of the mantle, one shell also is
only developed, while the other is stunted or placed under arrest. The
Snail's shell is one of the Bivalve Mollusc's shells, its operculum is
the other. This last is stony, horny, and finally is entirely wanting.
It is remarkable that the right shell has been pretty generally
perfected, while the left dwindles down into the operculum; all the
Snail's openings are therefore upon the right side, such as the anus,
with the orifices for the escape of the ova and semen.
Male animals are situated on the right side, female on the left; or
where the right side was predominating, there originated the male sex,
where the left, the female.
3218. As the orifice of the mantle and the shell is properly the
aperture of the branchial foramina; so can it be said, that the Snail
were a Mussel, which does not simply extend the foot, but also the
mouth or head to the branchial opening; it is a Mussel reversed.
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 tegumental fibres, 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 the
_calcareous 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, propels it 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 called _Cardiac 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
creatures _Nephritic_ or _Renal 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 called _Cylindrical Snails_, out of contrast to the _Sole_
and _Carinate Snails_ or 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 them _Kracken_.
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 into the 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 the _cylindrical
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 the _Annulate animals_.
The rings are to be regarded as cysts, which are mutually juxtaposited
or repeated, not being inserted within 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. _reticular_ in character; or
the branchiæ become individualized in certain situations and partly
horny, constituting _branchiæ_ proper; or finally, the tegument is
converted into an air-breathing organ, _tracheæ_ or _air-tubes_.
3232. It either feels with its whole surface, or by _papillæ_; or the
branchiæ change into horny _feet_; or lastly, into alary appendages or
_wings_. 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,
a _branchial network_ or _skin_.
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 a _Worm_.
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 the _Crustacea_ or
_Crabs_.
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 second class 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 the _Insecta_ proper or _Flies_.
3263. A Worm with feet, tracheæ and wings, is an _Entomon_ or _Insect_.
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 oesophagus, 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 of Insects; 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. Their abdomen 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, and wings. 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 is wanting 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 just liberated 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 its _metamorphosis_.
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, the _Fly_.
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, appear to 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. INTESTINAL ANIMALS. B. VASCULAR ANIMALS. C. RESPIRATORY ANIMALS.
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 a _Relationship of Proximity_,
as that between Infusoria, Polyps, and Acalephæ.
A _Relationship of Repetition_, as of Infusoria, Mussels, Worms.
There is also a _Relationship of Series_, which takes its rise from
the parallelism of the classes. The two last relationships have been
confounded together under the term _analogy_, 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 are _asarcose_ or _fleshless_ animals.
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, the _Fishes_.
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 coecum. This is very distinct in the
Sharks and Rays.
3316. In Birds therefore the vitelline canal is the coecum also, and
the two coeca, falsely so called, which are placed upon the side of
the rectum cannot represent the coecum 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 coecal 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 the trachea having taken place with the
oesophagus 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-cyst 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-cyst is the lung, in which, seeing that it
contains air, the blood is oxydized; this oxydized blood flows into the
heart and renders it _arteriose_ in 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.