52 PROCEEDINGS OF THE 



Jewish origin. Educated at the higli school and afterwards at 

 the Vniversityof Kharkoff, he was early attracted to Zoologj' and 

 published papers on Vorticella and on the nematode worm 

 Dij^logaster at the age of eighteen. In 1864 Metclniikoff went 

 to Geru)any to continue his researches in the laboratories of 

 von Siebold and Leuckart in Giessen and in Gottingen. At 

 this time he discovered the alternation of hermaphrodite and 

 bisexual generations in the nematode Rliahdonema nigrovenosa, 

 a common parasite of the frog's lung, and showed that the 

 hermaphrodite in the frog gives rise viviparously to a generation 

 of free-living males and females the fertilised eggs of which 

 infect a new host. Dissatisfied with his treatment by Leuckart, 

 Metc-hnikofF proceeded to Naples and then to Odessa, where he 

 jiiet the famous Eussian embryologist Kowalevsky, and in 1877 

 Mas made Professor in the University. It was during these 

 years that a series of papers appeared on Eotifers, Gastrotricha 

 and allied forms, and on the Siphonophora. Especially remark- 

 able were INJetchnikoff's contributions to embryology. He 

 described the vivipai'ous reproduction of the fly Cecidomyia, the 

 metamorphosis of the Actinntrocha larva into the adult Phoronis, 

 and of the Tornaria larva into Balanoglossus, determined the 

 Chsetopod affinities of the parasitic Myzostoma, and discovered the 

 embryonic membranes of Insects. A great deal of attention was 

 devoted to tracing the development of the germ-layers in various 

 Arthropods, Molluscs, Echinoderms, and Tunicates, and he was 

 the first to determine correctly the fate of the ciliated and 

 granular cells in the amphiblastula of Sponges. 



The great value and originality of tliese researches have, how- 

 ever, been somewhat overshadowed by tlie later work of 

 Metchnikoff wliich grew out of them. While studving minute 

 transparent aquatic forms and larvae, he was struck with the 

 importance of the freely-moving mesoblastic cells found wander- 

 ing throughout the spaces and tissues of the body. Combining 

 the scattered observations of others with the results of his own 

 patient researches, he concluded that these free amoeboid cells, 

 whether working their way through the tissues or floating in the 

 blood and lymi)h as white corpuscles, are active scavengers which 

 singly or in groups eat up and destroy decaying cells, foreign 

 intrusive substances, and invading organisms, such as bacteria 

 and other parasites. Just as an amoeba injects its food, so these 

 wandering cells or phagocytes, as Metchnikoff called them, take 

 in useless or injurious living or dead particles in multicellular 

 animals. To pursue his work on ])hagocyt()sis he left Odessa, 

 and went to Paris in 1888, where he was welcomed by Pasteur. 

 The great Frenchman had proved that parasitic bncteria are the 

 cause of most infectious diseases, and that inoculations with artificial 

 cultures of the offending organism may serve to prevent or to 

 cure the disease. It remained for Metchnikoff to explain how^ 

 immunity and recovery are brought ai)Out. In a masterly book 

 on Inflammation (1892) he traced the phagocytic action of cells 



