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Lamarck’s career as a botanist comprised about twenty-five years. We now come to the third stage of his life—Lamarck the zoölogist and evolutionist. He was in his fiftieth year when he assumed the duties of his professorship of the zoölogy of the invertebrate animals; and at a period when many men desire rest and freedom from responsibility, with the vigor of an intellectual giant Lamarck took upon his shoulders new labors in an untrodden field both in pure science and philosophic thought.

It was now the summer of 1793, and on the eve of the Reign of Terror, when Paris, from early in October until the end of the year, was in the deadliest throes of revolution. The dull thud of the guillotine, placed in front of the Tuileries, in the Place de la Revolution, which is now the Place de la Concorde, a little to the east of where the obelisk of Luxor now stands, could almost be heard by the quiet workers in the Museum, for sansculottism in its most aggressive and hideous forms raged not far from the Jardin des Plantes, then just on the border of the densest part of the Paris of the first Revolution. Lavoisier, the founder of modern chemistry, was guillotined some months later. The Abbé Haüy, the founder of crystallography, had been, the year previous, rescued from prison by young Geoffroy St. Hilaire, his neck being barely saved from the gleaming axe. Roland, the friend of science and letters, had been so hunted down that at Rouen, in a moment of despair, on hearing of his wife’s death, he thrust his sword-cane through his heart. Madame Roland had been beheaded, as also a cousin of her husband, and we can well imagine that these fateful summer and autumn days were scarcely favorable to scientific enterprises.[32] Still, however, amid the loud alarums of this social tempest, the Museum underwent a new birth which proved not to be untimely. The Minister of the Interior (Garat) invited the professors of the Museum to constitute an assembly to nominate a director and a treasurer, and he begged them to present extracts of their deliberations for him to send to the executive council, “under the supervision of which the National Museum is for the future placed;” though in general the assembly only reported to the Minister matters relating to the expenses, the first annual grant of the Museum being 100,000 livres.

Four days after, June 14th, the assembly met and adopted the name of the establishment in the following terms: Muséum d’Histoire Naturelle décrété par la Convention Nationale le 10 Juin, 1793; and at a meeting held on the 9th of July the assembly definitely organized the first bureau, with Daubenton as director, Thouin treasurer, and Desfontaines secretary. Lamarck, as the records show, was present at all these meetings, and at the first one, June 14th, Lamarck and Fourcroy were designated as commissioners for the formation of the Museum library.

All this was done without the aid or presence of Bernardin de Saint-Pierre, the Intendant. The Minister of the Interior, meanwhile, had communicated to him the decision of the National Convention, and invited him to continue his duties up to the moment when the new organization should be established. After remaining in his office until July 9th, he retired from the Museum August 7th following, and finally withdrew to the country at Essones.

The organization of the Museum is the same now as in 1793, having for over a century been the chief biological centre of France, and with its magnificent collections was never more useful in the advancement of science than at this moment.

Let us now look at the composition of the assembly of professors, which formed the Board of Administration of the Museum at the time of his appointment.

The associates of Lamarck and Geoffroy St. Hilaire, who had already been connected with the Royal Garden and Cabinet, were Daubenton, Thouin, Desfontaines, Portal, and Mertrude. The Nestor of the faculty was Daubenton, who was born in 1716. He was the collaborator of Buffon in the first part of his Histoire Naturelle, and the author of treatises on the mammals and of papers on the bats and other mammals, also on reptiles, together with embryological and anatomical essays. Thouin, the professor of horticulture, was the veteran gardener and architect of the Jardin des Plantes, and withal a most useful man. He was affable, modest, genial, greatly beloved by his students, a man of high character, and possessing much executive ability. A street near the Jardin was named after him. He was succeeded by Bosc. Desfontaines had the chair of botany, but his attainments as a botanist were mediocre, and his lectures were said to have been tame and uninteresting. Portal taught human anatomy, while Mertrude lectured on vertebrate anatomy; his chair was filled by Cuvier in 1795.

Of this group Lamarck was facile princeps, as he combined great sagacity and experience as a systematist with rare intellectual and philosophic traits. For this reason his fame has perhaps outlasted that of his young contemporary, Geoffroy St. Hilaire.

The necessities of the Museum led to the division of the chair of zoölogy, botany being taught by Desfontaines. And now began a new era in the life of Lamarck. After twenty-five years spent in botanical research he was compelled, as there seemed nothing else for him to undertake, to assume charge of the collection of invertebrate animals, and to him was assigned that enormous, chaotic mass of forms then known as molluscs, insects, worms, and microscopic animals. Had he continued to teach botany, we might never have had the Lamarck of biology and biological philosophy. But turned adrift in a world almost unexplored, he faced the task with his old-time bravery and dogged persistence, and at once showed the skill of a master mind in systematic work.

The two new professorships in zoölogy were filled, one by Lamarck, previously known as a botanist, and the other by the young Étienne Geoffroy St. Hilaire, then twenty-two years old, who was at that time a student of Haüy, and in charge of the minerals, besides teaching mineralogy with especial reference to crystallography.

To Geoffroy was assigned the four classes of vertebrates, but in reality he only occupied himself with the mammals and birds. Afterwards Lacépède[33] took charge of the reptiles and fishes. On the other hand, Lamarck’s field comprised more than nine-tenths of the animal kingdom. Already the collections of insects, crustacea, worms, molluscs, echinoderms, corals, etc., at the Museum were enormous. At this time France began to send out those exploring expeditions to all parts of the globe which were so numerous and fruitful during the first third of the nineteenth century. The task of arranging and classifying single-handed this enormous mass of material was enough to make a young man quail, and it is a proof of the vigor, innate ability, and breadth of view of the man that in this pioneer work he not only reduced to some order this vast horde of forms, but showed such insight and brought about such radical reforms in zoölogical classification, especially in the foundation and limitation of certain classes, an insight no one before him had evinced. To him and to Latreille much of the value of the Règne Animal of Cuvier, as regards invertebrate classes, is due.

The exact title of the chair held by Lamarck is given in the État of persons attached to the National Museum of Natural History at the date of the 1er messidor, an II. of the Republic (1794), where he is mentioned as follows: “Lamarck—fifty years old; married for the second time; wife enceinte; six children; professor of zoölogy, of insects, of worms, and microscopic animals.” His salary, like that of the other professors, was put at 2,868 livres, 6 sous, 8 deniers.[34]

Étienne Geoffroy St. Hilaire[35] has related how the professorship was given to Lamarck.

“The law of 1793 had prescribed that all parts of the natural sciences should be equally taught. The insects, shells, and an infinity of organisms—a portion of creation still almost unknown—remained to be treated in such a course. A desire to comply with the wishes of his colleagues, members of the administration, and without doubt, also, the consciousness of his powers as an investigator, determined M. de Lamarck: this task, so great, and which would tend to lead him into numberless researches; this friendless, unthankful task he accepted—courageous resolution, which has resulted in giving us immense undertakings and great and important works, among which posterity will distinguish and honor forever the work which, entirely finished and collected into seven volumes, is known under the name of Animaux sans Vertèbres.”

Before his appointment to this chair Lamarck had devoted considerable attention to the study of conchology, and already possessed a rather large collection of shells. His last botanical paper appeared in 1800, but practically his botanical studies were over by 1793.

During the early years of the Revolution, namely, from 1789 to and including 1791, Lamarck published nothing. Whether this was naturally due to the social convulsions and turmoil which raged around the Jardin des Plantes, or to other causes, is not known. In 1792, however, Lamarck and his friends and colleagues, Bruguière, Olivier, and the Abbé Haüy, founded the Journal d’Histoire Naturelle, which contains nineteen botanical articles, two on shells, besides one on physics, by Lamarck. These, with many articles by other men of science, illustrated by plates, indicate that during the years of social unrest and upheaval in Paris, and though France was also engaged in foreign wars, the philosophers preserved in some degree, at least, the traditional calm of their profession, and passed their days and nights in absorption in matters biological and physical. In 1801 appeared his Système des Animaux sans Vertèbres, preceded by the opening discourse of his lectures on the lower animals, in which his views on the origin of species were first propounded. During the years 1793–1798, or for a period of six years, he published nothing on zoölogy, and during this time only one paper appeared, in 1798, on the influence of the moon on the earth’s atmosphere. But as his memoirs on fire and on sound were published in 1798, it is evident that his leisure hours during this period, when not engaged in museum work and the preparation of his lectures, were devoted to meditations on physical and meteorological subjects, and most probably it was towards the end of this period that he brooded over and conceived his views on organic evolution.

It appears that he was led, in the first place, to conchological studies through his warm friendship for a fellow naturalist, and this is one of many proofs of his affectionate, generous nature. The touching story is told by Étienne Geoffroy St. Hilaire.[36]

“It was impossible to assign him a professorship of botany. M. de Lamarck, then forty-nine years old, accepted this change in his scientific studies to take charge of that which everybody had neglected; because it was, indeed, a heavy load, this branch of natural history, where, with so varied relations, everything was to be created. On one group he was a little prepared, but it was by accident; a self-sacrifice to friendship was the cause. For it was both to please his friend Bruguière as well as to penetrate more deeply into the affections of this very reserved naturalist, and also to converse with him in the only language which he wished to hear, which was restricted to conversations on shells, that M. de Lamarck had made some conchological studies. Oh, how, in 1793, did he regret that his friend had gone to Persia! He had wished, he had planned, that he should take the professorship which it was proposed to create. He would at least supply his place; it was in answer to the yearnings of his soul, and this affectionate impulse became a fundamental element in the nature of one of the greatest of zoölogical geniuses of our epoch.”

Once settled in his new line of work, Lamarck, the incipient zoölogist, at a period in life when many students of less flexible and energetic natures become either hide-bound and conservative, averse to taking up a different course of study, or actually cease all work and rust out—after a half century of his life had passed, this rare spirit, burning with enthusiasm, charged like some old-time knight or explorer into a new realm and into “fresh fields and pastures new.” His spirit, still young and fresh after nearly thirty years of mental toil, so unrequited in material things, felt a new stimulus as he began to investigate the lower animals, so promising a field for discovery.

He said himself:

“That which is the more singular is that the most important phenomena to be considered have been offered to our meditations only since the time when attention has been paid to the animals least perfect, and when researches on the different complications of the organization of these animals have become the principal foundation of their study. It is not less singular to realize that it was almost always from the examination of the smallest objects which nature presents to us, and that of considerations which seem to us the most minute, that we have obtained the most important knowledge to enable us to arrive at the discovery of her laws, and to determine her course.”

After a year of preparation he opened his course at the Museum in the spring of 1794. In his introductory lecture, given in 1803, after ten years of work on the lower animals, he addressed his class in these words:

“Indeed it is among those animals which are the most multiplied and numerous in nature, and the most ready to regenerate themselves, that we should seek the most instructive facts bearing on the course of nature, and on the means she has employed in the creation of her innumerable productions. In this case we perceive that, relatively to the animal kingdom, we should chiefly devote our attention to the invertebrate animals, because their enormous multiplicity in nature, the singular diversity of their systems of organization and of their means of multiplication, their increasing simplification, and the extreme fugacity of those which compose the lowest orders of these animals, show us, much better than the higher animals, the true course of nature, and the means which she has used and which she still unceasingly employs to give existence to all the living bodies of which we have knowledge.”

During this decade (1793–1803) and the one succeeding, Lamarck’s mind grew and expanded. Before 1801, however much he may have brooded over the matter, we have no utterances in print on the transformation theory. His studies on the lower animals, and his general knowledge of the vertebrates derived from the work of his contemporaries and his observations in the Museum and menagerie, gave him a broad grasp of the entire animal kingdom, such as no one before him had. As the result, his comprehensive mind, with its powers of rapid generalization, enabled him to appreciate the series from monad (his ébauche) to man, the range of forms from the simple to the complex. Even though not a comparative anatomist like Cuvier, he made use of the latter’s discoveries, and could understand and appreciate the gradually increasing complexity of forms; and, unlike Cuvier, realize that they were blood relations, and not separate, piece-meal creations. Animal life, so immeasurably higher than vegetable forms, with its highly complex physiological functions and varied means of reproduction, and the relations of its forms to each other and to the world around, affords facts for evolution which were novel to Lamarck, the descriptive botanist.