62 MORPHOGENESIS IN CILIATES 



Fremiet (19486) considers that ''it is the cihary system, 

 or, more precisely, the infracihature in the sense of Chatton 

 and Lwoff, which commands all the regenerative morpho- 

 genesis." Let us recall that the infraciliature is the sum of 

 kinetosomes. 



The study of morphogenesis, in very evolved ciliates, e.g., 

 Licnophora and Euplotes, will show later how, starting from 

 kinetosomes and other non-visible materials, a specific com- 

 plicated structure may be formed. Kinetosomes are the in- 

 struments of morphogenesis. The importance of the in^ 

 fraciliature is therefore not questionable. However, I 

 should like to point out that, if kinetosomes are necessary 

 for morphogenesis, they seem not to ''command" but to 

 obey some mysterious force which is responsible for their 

 orientation. Perhaps it is better to say that they cooperate 

 with some other factors, or that morphogenesis is the result 

 of the interaction of kinetosomes with other factors. This 

 problem will be discussed later on. 



Coming back to the problem of symmetry and equilib- 

 rium, I should like to add a few remarks to Faure-Fremiet's 

 important experiments and discussion. The cortical pattern 

 and especially the kinetial system are certainly important. 

 When considering many evolved ciliates and especially the 

 group of Thigmotricha, it is clear that the division "zone" 

 does not coincide with the theoretical equator of the organ- 

 ism, but "cuts" the kineties in their middle, even if they are 

 located on the anterior half of the parent [E. Chatton and 

 A. Lwoff (1949)]. The question naturally arises, and this 

 is not a purely academic discussion, whether it is not the 

 middle of the kinety which determines the position of the 

 constriction zone. This would mean a more or less "autono- 

 mous" equilibrium of the kinety. But studies of apostomes 

 have shown that the length of the kinety is controlled by 

 its environment, that is to say, by properties of the cortex 

 as a reflection of the metabolism. 



