Zoological Philosophy
by 
J. B. Lamarck

[This translation, which has been prepared by Ian Johnston of Malaspina University-College, Nanaimo, BC, Canada, is in the public domain and may be used by anyone, in whole or in part, without permission and without charge, provided the source is acknowledged, released April 2000]

First Part

Considerations of the Natural History of Animals, Their Characteristics, Their Interrelationships, Their Organic Structure, Their Distribution, Their Classification and Their Species

Chapter Eight

Concerning the natural order of animals and the structure we must give to their general distribution so that it conforms to the very order of nature.

I have already remarked (Chapter V) that the essential aim of a distribution of animals must not limit itself, on our part, to the possession of a list of classes, genera, and species. This distribution must at the same time display, in its structure, the means most favorable to the study of nature, something which is most relevant to make us understand her progress, her means, and her laws.

However, I do not hesitate to point out that our general distributions of animals up to the present day have been given a structure which reverses the very order nature followed in giving rise successively to her living productions. Thus, in moving, according to custom, from the most complex towards the most simple, we make knowledge of the progress in the composition of organic structure more difficult to grasp, and we put ourselves in the position of perceiving less easily both the causes of this progress and the interruptions here and there in it.

When we realize that something is useful, even that it is indispensable for the goal we propose and that there is nothing inconvenient about it, we must hurry to make use of it, even though it is contrary to custom.

Such is the case concerning the structure which we must give to the general disposition of animals.

Moreover, we will see that it is not at all an indifferent matter to begin this general distribution of animals at either one of its extremities and that what should come at the start of the order cannot be simply a matter of our choice.

The custom which was introduced and which people have followed up to the present day of putting at the head of the animal kingdom the most perfect animals and to finish this kingdom by the least perfect and the simplest in organic structure owes its origin, in part, to the tendency which makes us always give precedence to the objects which we find striking, which please us, or which interest us the most, and, in part, to the fact that we have preferred to move from the best known towards the least known.

At the time when people began to occupy themselves with the study of natural history, these considerations were, no doubt, very persuasive. But they ought to yield now to scientific needs and particularly to the need to facilitate our progress in the understanding of nature.

With respect to animals which nature has succeeded in producing, so numerous and so varied, if we cannot boast of knowing exactly the true order which nature followed in bringing them successively into existence, what I am going to reveal is probably very close to that order. Reason and all the knowledge we have acquired encourage this probability.

In fact, if it is true that all living bodies are productions of nature, we cannot refuse to believe that she could produce them only successively, not all at once at a specific moment. Now, if she created them one after the other, there is reason to believe that she began exclusively with the simplest and did not produce the most complex organic structures (in both the animal and plant kingdoms) until the end,

Botanists first gave zoologists the example of the true arrangement we should give to a general distribution in order to represent the very order of nature. For they formed the first class of plants with the acotyledonous or agamous plants, that is, with the structurally simplest plants, the most imperfect in every respect, in a word, with those which had no cotyledons, no determinable sex, no vessels in their tissues, plants which are, in fact, composed only of cellular tissue more or less modified according to different extensions.

What the botanists have done with respect to plants, we should finally do with the animal kingdom, not only because nature herself points in that direction and reason demands it, but also because the natural order of classes, according to the growing complexity in organic structure, is much easier to determine among the animals than it is with respect to plants.

While this order will better set down the order of nature, it will at the same time make the study of objects much easier, will improve our understanding of the organic structure of animals, the progress in its complexity from class to class, and will demonstrate even better the affinities existing between the different degrees in the make up of animal organization and the external difference which we most frequently use to characterize the classes, orders, families, genera, and species.

I add to these two considerations (whose basis one cannot seriously call into question) the fact that if nature, incapable of making organic structures which survive for ever, had not had the means of giving these bodies the capacity of reproducing themselves with other individuals which resembled them, replaced them, and perpetuate the race by the same means, she would have been forced to create directly all the races or rather she would have been able to create only one race in each organic order, one for the simplest and most imperfect animals and one for the simplest and most imperfect plants.

In addition, if nature had not been capable of the active processes of organization with the ability to make that very organic structure more and more complex, by increasing the mobile energy of fluid movement and thus organic movement, and if she had not preserved through reproduction all the progress in the composition of organic structures and all the acquired improvements, she should assuredly never have produced this multitude of infinitely varied animals and plants, so different from each other in the condition of their organic structures and capacities.

Finally, she would not have been able to create right at the first the most eminent animal faculties, for they do not arise except with the help of very complex organic systems. Nature had to prepare gradually the means of bringing into existence such organic systems.

Thus, to establish, with respect to living bodies, the state of things which we observe, the only thing nature had to produce directly (that is, without the combination of any organic action) was the simplest organic bodies, whether animals or plants. And she still reproduces these in the same way, every day, in favorable places and seasons. Now, by giving to these bodies which she herself created the capacity to feed themselves, to grow, to multiply, and to preserve each time the improvements they acquired in their organic structure and, finally, by passing on these same capacities to all the individuals produced by organic reproduction, over time, given the enormous diversity of always changing circumstances, the living bodies of all the classes and every order were, through these means, produced one after the other.

In considering the natural order of animals, the very marked gradation which exists in the growing complexity of their organic structure and the number as well as the improvement of their faculties is far from being a new truth, for even the Greeks were able to perceive it (1). But they were not able to lay bare the principles and proofs, because people then lacked the knowledge necessary to establish them.

Now, in order to facilitate the knowledge of the principles which have guided me in the exposition which I am about to make concerning this order of animals, and to better render perceptible this gradation which we observe in the complexity of their organic structure, from the most imperfect among them, who are at the head of the series, right up to the most perfect which conclude the series, I have divided into six very distinct stages all the styles of organic structure which we have recognized in the entire extent of the animal ladder.

Of these six stages, the four first ones include the animals without vertebrae, and hence the first ten classes of the animal kingdom, according to the new order which we are going to follow; the two last stages include all the vertebrate animals, and thus the four (or five) final classes of animals.

With the assistance of this method, it will be easy to study and to follow the march of nature in the production of the animals she has brought into existence, to distinguish, throughout the whole extent of the animal ladder, the progress attained in the complexity of organic structure, and to verify throughout the precision of the distribution or the appropriateness of the assigned ranks, by examining the known characteristics and facts of organic structure.

This is the way in which for several years in my lessons at the Museum I set out the invertebrates, always proceeding from the most simple towards the most complex.

In order to make the arrangement and the totality of the general series of animals more distinct, let us first present a table of the fourteen classes dividing the animal kingdom, limiting ourselves to a very simple exposition of their characteristics and the stages of organic structure which they include.

Table of the Distribution and Classification of Animals,

Following the order which conforms most closely to the order of nature

INVERTEBRATE ANIMALS

Classes

Such is the table of the fourteen classes established among the known animals, and arranged following the order which most closely approximates the order of nature. The arrangement of these classes is such that that we will always be forced to conform to it, even if we refuse to adopt the lines of separation which form them, because this arrangement is based on the analysis of the organic structure of the living bodies with which it deals. This consideration, of the first importance, establishes the affinities which exist among the objects making up each division and the rank of each one of these groups in the entire series.

People will never find solid reasons for changing this distribution in its entirety, for reasons which I am going to reveal. But we will be able to make changes in the details, and above all in the divisions subordinate to the classes, because the affinities between objects comprising the sub-divisions are more difficult to determine and assume a more arbitrary character.

Now, in order to make better understood how much this arrangement and distribution of animals conform to the very order of nature, I am going to reveal the general series of known animals, divided into its principal divisions, proceeding from the simplest towards the most complex, in accordance with the reasons indicated above.

My purpose, in this exposition, will be to put the reader in a position to recognize the rank, in the general series, occupied by the animals which, in the course of this work, I have often had occasion to refer to and to spare the reader the trouble of having to go to other works of zoology for that information.

However, I will give here only a simple list of genera and only of the principal divisions; but this list will be sufficient to demonstrate the extent of the general series, its arrangement conforming the most with the order of nature, and the indispensable placement of classes, orders, and thus, perhaps, of families and genera. We understand well that it is in the good works of zoology which we possess that we must study the details of all the objects mentioned in this list, because I have not taken that into consideration in this work.

General Distribution of Animals
Forming a series conforming to the very order of Nature

Invertebrate Animals

They do not have any vertebral column and consequently have no skeleton; those which have points of support for the movement of parts have them under their teguments. They lack a spinal chord and present a great diversity in the complexity of their organic structure.

First Stage of Organic Structure

No nerves, no longitudinal ganglionic chord, no vessels for circulation, no respiratory organs; no other special interior organ except for digestion.

[The Infusorians and Polyps]

THE INFUSORIANS
(First Class of the animal kingdom)

Fissiparous animals, amorphous, with gelatinous bodies, transparent, homogeneous, contractile and microscopic; no radiating tentacles; no rotary appendages; no special organ in the interior, not even for digestion.

Observations

Of all the known animals, the infusorians are the most imperfect, the simplest in organic structure, and those which possess the fewest capacities. It is certain they have no ability to feel.

Infinitely small, gelatinous, transparent, contractile, almost homogeneous, and incapable of having any special organ because of the excessively weak consistency of their parts, the infusorians are really only the rudiments of animal life.

These frail animals are the only ones which do not carry out digestion in order to nourish themselves and which, in fact, feed only by absorption through the pores of their skin and by an interior saturation.

In this matter they resemble the plants, which live only by absorption and carry out no digestion and whose organic movements operate only through external stimuli. But the infusorians are irritable and contractile, and they go through sudden movements which they can repeat several times in a row, something which characterizes their nature as animals and fundamentally distinguishes them from plants.

Table of Infusorians

First Order: Naked Infusorians

They lack external appendages

Second Order: Infusorians with Appendages

They have projecting parts, like hairs, types of horns or a tail

Cercaria
Trichocerca
Trichoda

Remarks. The monad, and especially the one which is called Monas termo, is the most imperfect and simplest of known animals, because its body, which is extremely small, displays only a gelatinous and transparent point, but it is contractile. This animal therefore must be considered the one at which the series of animals, organized according to nature, begins.

POLYPS
(Second Class of the Animal Kingdom)

Gemmiparous animals, with gelatinous regenerating bodies, without any interior organ except an alimentary canal with a single opening.  Terminal mouth surrounded by radiating tentacles or furnished with ciliated or rotatory organs.  The majority adhere to each other, communicate together by their alimentary canal, and thus form composite animals.

Observations

We saw in the infusorians infinitely small, frail animalcules without consistency, without a shape unique to their class, without any organs at all, and consequently without a mouth and a distinct alimentary canal.

In the polyps, the simplicity and imperfection of the organic structure, although still very noticeable, are less great than in the infusorians. Organic structure has clearly made some progress, for already nature has given the animals of this class a consistently regular form; already they are furnished with a special organ for digestion, and consequently with a mouth, the entry to their alimentary sack.

If we picture for ourselves a small elongated body, gelatinous, very irritable, having at its upper extremity a mouth furnished either with rotatory organs or radiating tentacles which serves as the entry point to an alimentary canal which has no other opening, we will get an image of the polyp.

If we add to this idea the notion of the adherence of several of these small bodies, living together and participating in a common life, we will understand the most general and the most remarkable fact concerning these animals.

Since the polyps have neither nerves for feeling nor special organs for respiration nor vessels for the circulation of their fluids, they are the more imperfect in their organic structure than the animals which are going to follow.

Table of Polyps

First Order: Rotifer Polyps

They have around their mouths ciliated and rotatory organs

Urceolaria
Brachionus (?)
Vorticella

Second Order: Polyps in Polyparies

They have around their mouths radiating tentacles and are fixed in a polypary which does not float on the oceans.

(1) Membranous or Horny polypary, without a distinct outer crust

(2) Polypary with a horny axis, covered with a crust

(3) Polypary with an axis and partly or entirely stony, and covered over with a bark like crust

Isis
Coral

(4) Polypary entirely stony without a crust

Third Order: Floating Polyps

A polypary free, elongated, floating in water, and having a horny or bony axis covered with a skin common to all the polyps; radiating tentacles around the mouth.

Fourth Order: Naked Polyps

They have radiating often multiple tentacles at their mouths; they do not form polyparies.

Second Stage of Organic Structure

No longitudinal ganglionic chord, no vessels for circulation; a few special internal organs (either tubes or pores taking in water or species of ovaries) other than those for digestion.

[The Radiates and Worms]

RADIATES

(Third Class of the Animal Kingdom)

Subgemmiparous animals, free or wandering; with regenerating bodies, a radiating arrangement of parts, both internal and external, and compound organ of digestion; lower mouth, simple or multiple.  No head, no eyes, no articulated limbs; a few internal organs other than those for digestion.

Observations

Here is the third line of classic separation which it is useful to draw in the natural distribution of animals.

Here we find entirely new forms which all nonetheless have affinities with a common similar type, as follows: the radiating arrangement of the parts, both interior and exterior.

These are no long animals with an elongated body, an upper terminal mouth, usually established in a polypary with a great number of them living together, each participating in a communal life. These are animals with a more complex organic structure than in the polyps, simple, always free, with a design which is unique to them, and generally orienting themselves in an inverted position.

Almost all the radiata have tubes drawing in water which appear to be aquatic trachaea. And in a great number we find special bodies which look like ovaries.

In a Memorandum which I have just heard read in the assembly of professors at the Museum, I learn than a wise observer, Doctor Spix, a Bavarian physician, has discovered in the star fishes and sea anemones the apparatus of a nervous system.

Doctor Spix claims to have observed that in the red star-fish, under a membrane made up of tendons (like a tent) there is suspended on the stomach a reticular structure made up of whitish nodules and threads and, in addition, at the origin of each ray, two nodules or ganglia which communicate with each other by a thread and from which other threads leave and go to parts close by; among others there are two very long threads which run through the full length of the ray and supply the tentacles.

According to the observations of this learned man, we see in each ray two nodules, a small extension of the stomach (coecum), two hepatic lobes, two ovaries and trachaeal canals.

In the sea-anemones, Dr. Spix observed at the base of these animals, below the stomach, a few pairs of nodules, arranged around a centre, which communicate with each other by cylindrical threads and which send out other threads to the upper parts. Moreover, he saw there four ovaries surrounding the stomach, from the base of which canals leave which, after joining up, open into a lower point of the alimentary canal.

It is astonishing that such a complex organic apparatus has escaped the attention of all those who have examined the organic structure of these animals.

If Doctor Spix was not imagining things in in what he believed he saw and if he was not wrong in attributing to these organisms a nature and functions different from what is appropriate to them (something which has happened to so many botanists who believed they saw male and female organs in almost all the cryptogram plants), then the consequences are as follows:

(1) It is not in the insects that we must establish the commencement of a nervous system;

(2) This system must be considered as rudimentary in the insects, radiates, and even in the sea-anemone, the last genre of polyps;

(3) This is not a reason why all polyps should possess the rudiments of this system, in the same way that it does not follow that all reptiles are equipped with bills just because some have them.

(4) Finally, the nervous system is no less a special organ, not shared by all living bodies. For not only is it irrelevant in plants but it it is not even present in all the animals. As I have made known, it is impossible that the infusorians are furnished with a nervous system and assuredly polyps in general are not capable of having one. Thus, we would look for it in vain in the hydras, which nonetheless belong to the last order of polyps, the one closest to the radiates, since it includes the sea anemones.

Thus, whatever the basis for the facts cited above, the points which I present in this work on the successive formation of the different special organs remain valid no matter at what point in the animal scale each of these organs originates. And it is always the case that the abilities which the organs provide for the animal do not begin to operate until the organ which provides them come into existence.

Table of Radiates

First Order: Soft Radiates

Gelatinous body; soft skin, transparent, lacking articulated spines; no anus.

Second Order: Echinoderm Radiates

Opaque skin, crustaceous or coriaceous, furnished with retractable tubercules or articulates spines on tubercules, and pierced with holes in a series.

(1) Stellerides. Skin not irritable, but mobile; no anus

Ophiura
Asteria

(2) Echinoids. Skin not irritable, not mobile; an anus

(3) Fistulides. Elongated body, an irritable and mobile skin; an anus

Holothuria
Sipunculus

Remarks. The sipunculus are animals very close to worms. However their known affinities with the holothuria have led them to be placed among the radiates, with which they no longer share characteristics. Consequently, they must come at the end.

In general, in a really natural distribution, the first and the last genera of classes are those in which the classical characteristics are less pronounced. Because they come at the limits of the class and the lines of separation are artificial, these genera must display to a lesser extent than the others the characteristics of their class.

WORMS

(Fourth Class in the Animal Kingdom)

Suboviparous animals, with soft elongated bodies, without a head, eyes, limbs, or bunches of setae; without circulation and with a complete intestinal canal (one with two openings).  Mouth made up of one or several suckers.

Observations

The general form of worms is very different from that of the radiates. Their mouths, always a sucker, has no similarity to those of the polyps, which display only an aperture accompanied by radiating tentacles or rotatory organs.

Worms have, in general, an elongated body, very slightly contractile, although very soft, and their intestinal canal is not limited to a single opening.

In the fistulid radiates, nature began to abandon the radiating form of the parts and to give animal bodies an elongated shape, the only one which might lead to the goal which nature set for herself.

Once nature created the worms, she is going to tend from that point on to establish the pattern of the paired symmetry of parts, which she could not attain except by an articulated design. But in the class of worms, which is ambiguous to some extent, she has only sketched out a few traits.

Table of Worms

First Order: Cylindrical Worms

Second Order: Bladder Worms

Bicorn
Hydatis

Third Order: Flat Worms

Third Stage of Organic Structure

Nerves ending in a longitudinal ganglionic chord; respiration by aerated trachaea; no circulation (or imperfect).

[The Insects and Arachnids]

INSECTS

(Fifth Class of the animal kingdom)

Oviparous animals, undergoing metamorphoses, able to have wings, and possessing, in the perfect state, six articulated limbs, two antennae, two faceted eyes, and a horny skin.  Respiration by aerated trachaea which extend to all the parts; no system of circulation; two distinct sexes; one single reproductive act in a lifetime.

Observations

Having reached the insects, we find among the extremely numerous animals which this class includes a very different order of things from the classes which we have have encountered in the animals of the four preceding classes.  Moreover, in the place of modulations in the progressive complexity of the organic structure in animals, once we arrive at the insects, in this matter we have made quite a considerable leap.

Here, for the first time, the animals examined from the outside show us a true head which is always distinct, very remarkable eyes (although still very imperfect), articulated limbs arranged in two rows, and the symmetrical form of paired and opposing parts which nature will use from this point on right up to and including the most perfect animals.

When we move to the interior of insects, we see in addition a complete nervous system, consisting of nerves which end a a longitudinal ganglionic chord.  Although complete, this nervous system is still very imperfect.  The area where the sensations meet appears very fractured, and the senses themselves are few and very obscure.  Finally, we see in the interior of the insect a real muscular system and distinct sexes, which, however, can provide only a single fertilization (as with the plants).

True, we do not yet find a circulatory system, and it is necessary to go higher in the animal chain to find this improvement in organic structure.

The property of all insects is having wings in their perfect state, so that those which lack them have been deprived only by an abortion which has become habitual and constant.

Observations

In the table which I am going to present, the genera have been reduced to a number considerably lower that that of the genera which people have made from the animals in this class.  Interest in studying the subject and the simplicity and the clarity of the method seemed to me to demand this reduction, which is not going to harm at all an understanding of the objects.  To use all the particular details which one could seize upon in the characteristics of animals and plants in order to multiply genera to infinity is, as I have already said, to clutter up and obscure science instead of serving it.  It makes the study of science so complicated and difficult, that it would become impossible to practice it, except for those who wished to dedicate their entire lives to learning the immense nomenclature and the minute characteristics used to make distinctions among animals.

Table of Insects

A. SUCKING INSECTS

Their mouths display a sucker furnished or lacking a sheath

First Order: Apterous Insects

A proboscis with two valves and articulated in three places, containing a sucking organ with two bristles  The wings have usually aborted in both sexes; legless larvae; immobile nymph in a cocoon.

Flea

Second Order: Dipterous Insects

A non-articulated proboscis, straight or with an elbow, sometimes retractile.  Two bare wings membranous and veined; two balancers; vermiform larvae, most often without feet 

Third Order: Hemipterous Insects

Sharp articulated beak, curved under the chest serving as a sheath for a sucker with three bristles.  Two wings hidden under membranous elytra; larvae with six feet; the nymph moves and eats.

Fourth Order: Lepidopterous Insects

A two-part sucker, lacking a sheath, like a tubular proboscis, and folded up as a spiral when inactive.  Four membranous wings, covered with colour scales like flour.  The larvae have eight to sixteen limbs, inactive chrysalis.

(1) With subulate or setaceous antennae

(2) Antennae swollen somewhere along their length

(B) BITING INSECTS

Their mouths display mandibles, most often accompanied by jaws

Fifth Order: Hymenopterous Insects

Mandibles and a three-sectioned sucker more or less extended, the base of which is enclosed in a short sheath.  Four bare wings (membranous, veined, unequal); in the female the anus is equipped with a sting or apparatus for boring; immobile nymph.

(1) Females equipped with a sting in the anus

(2) Females equipped with a boring apparatus in the anus

Sixth Order: Neuopterous Insects

Mandibles and jaws; four naked wings (membranous and reticulated); lengthened abdomen, lacking a sting or boring apparatus; six-footed larva; variation in the metamorphoses.

(1) Inactive nymphs