Lamarck, the Founder of Evolution Part 17

He agrees with Cuvier in placing the molluscs at the head of the invertebrates, a course still pursued by some zoologists at the present day. He states in the _Philosophie Zoologique_[122] that in his course of lectures of the year 1799 he established the cla.s.s of Crustacea, and adds that "although this cla.s.s is essentially distinct, it was not until six or seven years after that some naturalists consented to adopt it."

The year following, or in his course of 1800, he separated from the insects the cla.s.s of Arachnida, as "easy and necessary to be distinguished." But in 1809 he says that this cla.s.s "is not yet admitted into any other work than my own."[123] As to the cla.s.s of Annelides, he remarks: "Cuvier having discovered the existence of arterial and venous vessels in different animals which have been confounded under the name of worms (_Vers_) with other animals very differently organized, I immediately employed the consideration of this new fact in rendering my cla.s.sification more perfect, and in my course of the year 10 (1802) I established the cla.s.s of Annelides, a cla.s.s which I have placed after the molluscs and before the crustaceans, as their known organization requires." He first established this cla.s.s in his _Recherches sur les corps vivans_ (1802), but it was several years before it was adopted by naturalists.

The next work in which Lamarck deals with the cla.s.sification of the invertebrates is his _Discours d'ouverture du Cours des Animaux sans Vertebres_, published in 1806.

On page 70 he speaks of the animal chain or series, from the monad to man, ascending from the most simple to the most complex. The monad is one of his _Polypes amorphs_, and he says that it is the most simple animal form, the most like the original germ (_ebauche_) from which living bodies have descended. From the monad nature pa.s.ses to the Volvox, Proteus (Amoeba), and Vibrio. From them are derived the _Polypes rotiferes_ and other "Radiaires," and then the Vers, Arachnides, and Crustacea. On page 77 a tabular view is presented, as follows:

1. _Les Mollusques._ 2. _Les Cirrhipedes._ 3. _Les Annelides._ 4. _Les Crustaces._ 5. _Les Arachnides._ 6. _Les Insectes._ 7. _Les Vers._ 8. _Les Radiaires._ 9. _Les Polypes._

It will be seen that at this date two additional cla.s.ses are proposed and defined--_i.e._, the Annelides and the Cirrhipedes, though the cla.s.s of Annelida was first privately characterized in his lectures for 1802.

The elimination of the barnacles or Cirrhipedes from the molluscs was a decided step in advance, and was a proof of the acute observation and sound judgment of Lamarck. He says that this cla.s.s is still very imperfectly known and its position doubtful, and adds: "The Cirrhipedes have up to the present time been placed among the molluscs, but although certain of them closely approach them in some respects, they have a special character which compels us to separate them. In short, in the genera best known the feet of these animals are distinctly articulated and even crustaceous (_crustaces_)." He does not refer to the nervous system, but this is done in his next work. It will be remembered that Cuvier overlooked this feature of the jointed limbs, and also the crustaceous-like nervous system of the barnacles, and allowed them to remain among the molluscs, notwithstanding the decisive step taken by Lamarck. It was not until many years after (1830) that Thompson proved by their life-history that barnacles are true crustacea.

In the _Philosophie zoologique_ the ten cla.s.ses of the invertebrates are arranged in the following order:

_Les Mollusques._ _Les Cirrhipedes._ _Les Annelides._ _Les Crustaces._ _Les Arachnides._ _Les Insectes._ _Les Vers._ _Les Radiaires._ _Les Polypes._ _Les Infusoires._

At the end of the second volume Lamarck gives a tabular view on a page by itself (p. 463), showing his conception of the origin of the different groups of animals. This is the first phylogeny or genealogical tree ever published.

TABLEAU

Servant a montrer l'origine des differens animaux.

Vers. Infusoires.

. Polypes.

. Radiaires.

. Insectes.

. Arachnides.

Annelides. Crustaces.

Cirrhipedes.

Mollusques.

Poissons.

Reptiles.

Oiseaux. .

Monotremes. M. Amphibies.

. . M. Cetaces.

. M. Ongules.

M. Onguicules.

The next innovation made by Lamarck in the _Extrait du Cours de Zoologie_, in 1812, was not a happy one. In this work he distributed the fourteen cla.s.ses of the animal kingdom into three groups, which he named _Animaux Apathiques_, _Sensibles_, and _Intelligens_. In this physiologico-psychological base for a cla.s.sification he unwisely departed from his usual more solid foundation of anatomical structure, and the results were worthless. He, however, repeats it in his great work, _Histoire naturelle des Animaux sans Vertebres_ (1815-1822).

The sponges were by Cuvier, and also by Lamarck, accorded a position among the Polypes, near Alcyonium, which represents the latter's _Polypiers empates_; and it is interesting to notice that, for many years remaining among the Protozoa, meanwhile even by Aga.s.siz regarded as vegetables, they were by Haeckel restored to a position among the Coelenterates, though for over twenty years they have by some American zoologists been more correctly regarded as a separate phylum.[124]

Lamarck also separated the seals and morses from the cetacea. Adopting his idea, Cuvier referred the seals to an order of carnivora.

Another interesting matter, to which Professor Lacaze-Duthiers has called attention in his interesting letter on p. 77, is the position a.s.signed _Lucernaria_ among his _Radiaires mola.s.ses_ near what are now Ctenophora and Medusae, though one would have supposed he would, from its superficial resemblance to polyps, have placed it among the polyps.

To Lamarck we are also indebted for the establishment in 1818 of the molluscan group of Heteropoda.

Lamarck's acuteness is also shown in the fact that, whereas Cuvier placed them among the acephalous molluscs, he did not regard the ascidians as molluscs at all, but places them in a cla.s.s by themselves under the name of _Tunicata_, following the Sipunculus worms. Yet he allowed them to remain near the Holothurians (then including Sipunculus) in his group of _Radiaires echinodermes_, between the latter and the Vers. He differs from Cuvier in regarding the tunic as the h.o.m.ologue of the sh.e.l.l of Lamellibranches, remarking that it differs in being muscular and contractile.

Lamarck's fame as a zoologist rests chiefly on this great work. It elicited the highest praise from his contemporaries. Besides containing the innovations made in the cla.s.sification of the animal kingdom, which he had published in previous works, it was a summary of all which was then known of the invertebrate cla.s.ses, thus forming a most convenient hand-book, since it mentioned all the known genera and all the known species except those of the insects, of which only the types are mentioned. It pa.s.sed through two editions, and still is not without value to the working systematist.

In his _Histoire des Progres des Sciences naturelles_ Cuvier does it justice. Referring to the earlier volume, he states that "it has extended immensely the knowledge, especially by a new distribution, of the sh.e.l.led molluscs ... M. de Lamarck has established with as much care as sagacity the genera of sh.e.l.ls." Again he says, in noticing the three first volumes: "The great detail into which M. de Lamarck has entered, the new species he has described, renders his work very valuable to naturalists, and renders most desirable its prompt continuation, especially from the knowledge we have of means which this experienced professor possesses to carry to a high degree of perfection the enumeration which he will give us of the sh.e.l.ls" (_Oeuvres completes de Buffon_, 1828, t. 31, p. 354).

"His excellences," says Cleland, speaking of Lamarck as a scientific observer, "were width of scope, fertility of ideas, and a preeminent faculty of precise description, arising not only from a singularly terse style, but from a clear insight into both the distinctive features and the resemblance of forms" (_Encyc. Britannica_, Art. LAMARCK).

The work, moreover, is remarkable for being the first one to begin with the simplest and to end with the most highly developed forms.

Lamarck's special line of study was the Mollusca. How his work is still regarded by malacologists is shown by the following letter from our leading student of molluscs, Dr. W. H. Dall:

"SMITHSONIAN INSt.i.tUTION, "UNITED STATES NATIONAL MUSEUM, WASHINGTON, D. C., "_November 4, 1899._

"Lamarck was one of the best naturalists of his time, when geniuses abounded. His work was the first well-marked step toward a natural system as opposed to the formalities of Linne. He owed something to Cuvier, yet he knew how to utilize the work in anatomy offered by Cuvier in making a natural cla.s.sification. His failing eyesight, which obliged him latterly to trust to the eyes of others; his poverty and trials of various kinds, more than excuse the occasional slips which we find in some of the later volumes of the _Animaux sans Vertebres_. These are rather of the character of typographical errors than faults of scheme or principle.

"The work of Lamarck is really the foundation of rational natural malacological cla.s.sification; practically all that came before his time was artificial in comparison. Work that came later was in the line of expansion and elaboration of Lamarck's, without any change of principle. Only with the application of embryology and microscopical work of the most modern type has there come any essential change of method, and this is rather a new method of getting at the facts than any fundamental change in the way of using them when found. I shall await your work on Lamarck's biography with great interest.

"I remain, "Yours sincerely, "WILLIAM H. DALL."

FOOTNOTES:

[119] During the same period (1803-1829) Russia sent out expeditions to the North and Northeast, accompanied by the zoologists Tilesius, Langsdorff, Chamisso, Eschscholtz, and Brandt, all of them of German birth and education. From 1823 to 1850 England fitted up and sent out exploring expeditions commanded by Beechey, Fitzroy, Belcher, Ross, Franklin, and Stanley, the naturalists of which were Bennett, Owen, Darwin, Adams, and Huxley. From Germany, less of a maritime country, at a later date, Humboldt, Spix, Prince Wied-Neuwied, Natterer, Perty, and others made memorable exploring expeditions and journeys.

[120] These papers have been mercilessly criticised by Blainville in his "Cuvier et Geoffroy St. Hilaire." In the second article--_i.e._, on the anatomy of the limpet--Cuvier, in considering the organs, follows no definite plan; he gives a description "_tout-a-fait fantastique_" of the muscular fibres of the foot, and among other errors in this first essay on comparative anatomy he mistakes the tongue for the intromittent organ; the salivary glands, and what is probably part of the brain, being regarded as the testes, with other "_erreurs materielles inconcevables, meme a l'epoque ou elle fut redigee_." In his first article he mistakes a species of the myriapod genus Glomeris for the isopod genus Armadillo. In this he is corrected by the editor (possibly Lamarck himself), who remarks in a footnote that the forms to which M. Cuvier refers under the name of Armadillo are veritable species of Julus. We have verified these criticisms of Cuvier by reference to his papers in the "Journal." It is of interest to note, as Blainville does, that Cuvier at this period admits that there is a pa.s.sage from the Isopoda to the armadilloes and Julus. Cuvier, then twenty-three years old, wrote: "_Nous sommes donc descendus par degres, des ecrevisses aux Squilles, de celles-ci aux Aselles, puis aux Cloportes, aux Armadilles et aux ules_" (_Journal d'Hist. nat._, tom. ii., p. 29, 1792). These errors, as regards the limpet, were afterwards corrected by Cuvier (though he does not refer to his original papers) in his _Memoires pour servir a l'Histoire et a l'Anatomie des Mollusques_ (1817).

[121] _Tableau elementaire de l'Histoire naturelle des Animaux._ Paris, An VI. (1798). 8vo, pp. 710. With 14 plates.

[122] Tome i., p. 123.

[123] In his _Histoire des Progres des Sciences naturelles_ Cuvier takes to himself part of the credit of founding the cla.s.s Crustacea, stating that Aristotle had already placed them in a cla.s.s by themselves, and adding, "_MM. Cuvier et de Lamarck les en out distingues par des caracteres de premier ordre tires de leur circulation._" Undoubtedly Cuvier described the circulation, but it was Lamarck who actually realized the taxonomic importance of this feature and placed them in a distinct cla.s.s.

[124] See A. Hyatt's _Revision of North American Poriferae_, Part II.