2 MORPHOGENESIS IN CILIATES 



But Protozoa are, as stated by C. Dobell (1911), ''non- 

 cellular" organisms. A cell is a differentiated part of an 

 organism. Protozoa are complete individuals, whole organ- 

 isms, and behave as such. If one wants to remark the fact 

 that they generally have one nucleus, it is best to say that 

 they are monoenergid. 



The fundamental morphological and biochemical similar- 

 ity of living beings makes it probable that some processes 

 of morphogenesis, differentiation, and evolution in Protozoa 

 must have something in common with the homologous proc- 

 esses in Metazoa. 



How did the Protozoa, and especially the ciliates, manage 

 to reconcile the non-cellular state with such processes as dif- 

 ferentiation, development, morphogenesis, evolution, and 

 reproduction, some of which are antagonistic and irrevers- 

 ible? This is our main problem. It will be discussed in 

 terms of particulate phenomena. 



Numerous data concerning development have led embry- 

 ologists to the conclusion that cell differentiation must be 

 attributed to the unequal distribution and segregation of 

 specific particulate material. ''During the development," 

 writes R. Harrison (1937), "all movements, differentiation, 

 and in fact all developmental processes are actually effected 

 by the cytoplasm." 



The importance of specific cytoplasmic units in the life 

 of organisms and especially in developmental functions 

 seems thus to be well recognized. Cytoplasm is not just a 

 collection of enzymes or a plastic and complaisant receptor 

 passively submitted to the dictatorship of genes, but cer- 

 tainly contains self-reproducing bodies endowed with speci- 

 ficity. And the geneticists have indeed concluded that some 

 specific determinants do exist in the cytoplasm and play 

 their role in heredity. 



As a matter of fact, according to E. Caspari's review 

 (1948), some twenty cases of cytoplasmic inheritance have 



