Having had a bursa of 1600 roubles a year granted him for two years by the Russian Ministry of Public Instruction, he was able to undertake a journey to the shores of the Mediterranean in order to pursue his researches.
He had heard of a very talented young zoologist, Alexander Kovalevsky, who also knew him by hearsay and had written him a letter full of enthusiasm concerning the rich Mediterranean fauna and the facilities for work in Italy. He therefore went to Naples on leaving Giessen. Though the journey in itself had but a secondary attraction for him, he had expected to receive a strong impression; but his imagination had painted such grandiose pictures of the country that he had to cross, that the reality disappointed him, and Italy, like Switzerland on a former occasion, fell very far short of his expectations. He stopped at Florence, which made but a poor impression on him. Museums fatigued him, for he saw a great deal too many works of art all at once without any previous preparation. Architecture and the plastic arts in general did not take any hold of him. During his rapid journey he only saw the country quite superficially and had no time to become impregnated with its beauty. He therefore hastened towards Naples, where his work and Kovalevsky attracted him far more.
He found in Kovalevsky a young man with shy but cordial manners and the clear sweet eyes of a pure child, obviously an idealist. He had for science an absolute cult, the sacred fire of the worshipper; no sacrifice was too great, no difficulty too repellent for his ardour. On a closer acquaintance, the small, timid young man proved to be a hard fighter where science was concerned. The two young men formed an excellent impression of each other, and a friendship was started between them which was to last a lifetime. Though very different from each other, they met on common ground, a passion for science. They worked with the greatest energy, going together on zoological excursions, exchanging their ideas, discussing their aspirations; a similarity of tastes lent great attraction to their friendship.
At Giessen, Elie had read Fritz Müller’s For Darwin, a book which had a decisive influence on the future direction of his researches. Fritz Müller, in his embryological works on certain crustaceans, had been the first to confirm in a concrete manner Darwin’s evolutionist theories; he had thus demonstrated that it was chiefly in embryology that precious indications were to be found concerning the genealogy of organisms.[9] Under the influence of this work, Elie, who until now had limited himself to introductory researches, resolved to concentrate all his efforts on the comparative embryology of animals. He started to work in that direction, and his researches confirmed him more and more in the opinion that the key of animal evolution and genealogy was to be sought for in the most primitive stages, in those simple phases of development where no secondary element has yet been introduced from external conditions. In those primordial stages, essential characters, common to all, reveal the analogy and connections between animals from different groups.
Every animal begins by being unicellular, for the egg-cell, the reproducing cell, common to all, corresponds to a unicellular being. It is only after fecundation, when it has become an ovum, that this first cell evolves by dividing itself into consecutive segments, each of which is a new cell. This phenomenon is analogous with the multiplication of unicellular beings through division; only, those segments of the ovum do not separate but constitute a whole under the aspect of a hollow sphere, called a blastula, which is the first manifestation of a multicellular being. This blastula is formed of superposed layers, each of which gives birth to specialised organs in the embryo. The outside layer, or ectoderm, produces teguments and the nervous system; the internal layer, or endoderm, gives birth to endothelial cells, the digestive and internal organs; between those two layers comes a third, intermediary layer, the mesoderm, from which the skeleton is developed and also the muscle and blood tissues.
The evolution of these layers in Vertebrates was well known, but very little so in Invertebrates, though it is only through the development of inferior forms that the origin and general evolution of living beings can be elucidated. That is why, during many years, the principal theme of Metchnikoff’s researches was the comparative study of the embryonic layers of inferior animals and the ulterior fate of their constituting elements. By following this train of thought, he was able to demonstrate that the development of lower animals takes place on the same plan and follows the same laws as that of higher animals; thus, that there is a real communion between all living beings, which is the concrete confirmation of the theory of evolution.
By their work, Kovalevsky and Metchnikoff contributed to the foundation of Comparative Embryology. The comparative study of cells produced from the divers embryonic layers, and observations on the ulterior development of the functions of those cells, gradually led Metchnikoff to his theory of phagocytes and to pathological biology. An uninterrupted thread can be followed right through his life-work, from the beginning until the end.
In spite of his absorbing work he took great interest in his surroundings, and during this first stay in Italy he became acquainted with two interesting personalities, Bakounine the anarchist and the celebrated physiologist Setchénoff. Both resided at Sorrento. Kovalevsky and Metchnikoff, who greatly desired to know them, decided to call on them, after much hesitation.
Bakounine, a giant with a leonine head and a thick mane of grey hair, struck them as being a fiery enthusiast but an intolerant sectarian, easily roused; for instance, any small and unimportant local meeting was enough for him to predict an imminent revolution in Russia. His theories were epitomised in these words, “We must not leave stone upon stone”; but when asked what should be built up on those ruins he could only say, “We shall see later.” Elie looked upon him as a force powerful by its fire and vitality, but thought his mind neither judicial nor profound.