110 LIFE OF ELIE METCHNIKOFF 



" parenchymula " stage of development. He therefore 

 gave to that hypothetical ancestor the name of 

 parenchymella. 



Later, in 1886, he definitely formulated his theory 

 of the genesis of multicellular beings, and having 

 already stated the phagocyte theory, he substituted 

 for the name parenchymella that of phagocytella, which 

 indicated at the same time the primitive mode of 

 digestion of that hypothetical ancestor. 



Reduced to its simplest form, it presented, accord- 

 ing to Metchnikoff, a certain analogy with a colony 

 composed of unicellular beings of two kinds : the 

 first, flagellated, forming the external layer, and the 

 others, amoeboid, occupying the centre of the colony 

 and capable of digesting. 



It may be interesting to mention here that, in this 

 hypothetical description, Metchnikoff foresaw the 

 existence of similar, but real, beings discovered a year 

 later by Saville Kent, namely, the flagellated colonies 

 of Protospongia. 



Thus the link between the unicellular and the 

 multicellular beings could be constituted through the 

 intermediary of flagellated colonies on the one hand 

 and, on the other hand, of beings similar to a phago- 

 cytella. The indivisible colony became the muUi- 

 cellular individual. 



While studying the genealogy of beings, Metch- 

 nikoff continued his researches on intracellular diges- 

 tion. In 1879, at Naples and at Messina, he was 

 able to establish the fact that the mesodermic cells 

 of many larvae of Echinodermata and Ccelenterata, 

 endowed with a digestive tube, nevertheless contained 

 strange bodies. Therefore, even complicated organ- 

 isms with a differentiated digestive system could still 



