Though not a comparative anatomist, he at once perceived the value of a knowledge of the internal structure of animals, and made effective use of the discoveries of Cuvier and of his predecessors—in fact, basing his system of classification on the organs of respiration, circulation, and the nervous system.
He intimated that specific characters vary most, and that the peripheral parts of the body, as the shell, outer protective structures, the limbs, mouth-parts, antennæ, etc., are first affected by the causes which produce variation, while he distinctly states that it requires a longer time for variations to take place in the internal organs. On the latter he relied in defining his classes.
One is curious to know how Lamarck viewed the question of species. This is discussed at length by him in his general essays, which are reproduced farther on in this biography, but his definition of what a species is far surpasses in breadth and terseness, and better satisfies the views now prevailing, than that of any other author.
His definition of a species is as follows:
“Every collection of similar individuals, perpetuated by generation in the same condition, so long as the circumstances of their situation do not change enough to produce variations in their habits, character, and form.”
Lamarck’s rare skill, thoroughness, and acuteness as an observer, combined with great breadth of view, were also supplemented by the advantages arising from residence in Paris, and his connection with the Museum of Natural History. Paris was in the opening years of the nineteenth century the chief centre of biological science. France having convalesced from the intestinal disorders of the Revolution, and, as the result of her foreign wars, adding to her territory and power, had begun with the strength of a young giant to send out those splendid exploring expeditions which gathered in collections in natural history from all parts of the known or accessible world, and poured them, as it were, into the laps of the professors of the Jardin des Plantes. The shelves and cases of the galleries fairly groaned with the weight of the zoölogical riches which crowded them. From the year 1800 to 1832 the French government showed the greatest activity in sending out exploring expeditions to Egypt, Africa, and the tropics.[119]
The zoölogists who explored Egypt were Geoffroy St. Hilaire and Savigny. Those who visited the East, the South Seas, the East Indian archipelago, and other regions were Bruguière, Olivier, Bory de St. Vincent, Péron, Lesueur, Quoy, Gaimard, Le Vaillant, Edoux, and Souleyet. The natural result was the enormous collections of the Jardin des Plantes, and consequently enlarged views regarding the number and distribution of species, and their relation to their environment.
In Paris, about the time of Lamarck’s death, flourished also Savigny, who published his immortal works on the morphology of arthropods and of ascidians; and Straus-Durckheim, whose splendidly illustrated volumes on the anatomy of the cockchafer and of the cat will never cease to be of value; and É. Geoffroy St. Hilaire, whose elaborate and classical works on vertebrate morphology, embryology, and comparative anatomy added so much to the prestige of French science.
We may be sure that Lamarck did his own work without help from others, and gave full credit to those who, like Defrance or Bruguière, aided or immediately preceded him. He probably was lacking in executive force, or in the art which Cuvier knew so well to practise, of enlisting young men to do the drudgery or render material aid, and then, in some cases, neglecting to give them proper credit.
The first memoir or paper published on a zoölogical subject by Lamarck was a modest one on shells, which appeared in 1792 in the Journal d’Histoire naturelle, the editors of which were Lamarck, Bruguière, Olivier, Haüy, and Pelletier. This paper was a review of an excellent memoir by Bruguière, who preceded Lamarck in the work of dismemberment of the Linnæan genera. His next paper was on four new species of Helix. To this Journal, of which only two volumes were published, Cuvier contributed his first paper—namely, on some new species of “Cloportes” (Oniscus, a genus of terrestrial crustacea or “pill-bugs”); this was followed by his second memoir on the anatomy of the limpet, his next article being descriptions of two species of flies from his collection of insects.[120] Seven years later Lamarck gave some account of the genera of cuttlefishes. His first general memoir was a prodromus of a new classification of shells (1799).