80 MORPHOGENESIS IN CILIATES 



The large network of an adult Euplotes also seems a rigid 

 structure, able to disappear only when replaced by the 

 newly formed meshes which enlarge or ''grow" during mor- 

 phogenesis of the daughter organisms. The "rigidity" of 

 the differentiated network is shown by starvation experi- 

 ments with the hypotrich Stylonychia mytilus, during which 

 the size of the organism decreases. The organism is re- 

 peatedly reorganized into a smaller organism during this 

 process [Dembowska (1938)]. 



We encounter great difficulties when we try to define 

 what may be considered as specific phenomena of a dividing 

 ciliate from the purely morphological point of view. 



To analyze division in a very simple organism like a prim- 

 itive flagellate possessing one flagellum seems easy. Divi- 

 sion of the kinetosome is one of the first visible signs, and 

 precedes nuclear and cytoplasmic division. Some conditions 

 induce the division of one self-reproducing organelle. But 

 this does not mean that the division of self-reproducing or- 

 ganelles is responsible for the division of the organism. 



In Gyvinodinioides, elongation of kineties a, x, y, z takes 

 place before division and seems ''specific" of division. Ob- 

 viously, some morphogenetic material induces the division 

 of the kinetosomes of these four ciliary rows. Synthesis of 

 some "morphogenetic material" thus appears as one of the 

 important phenomena preceding division. But one could 

 object that in regeneration also there is synthesis of mor- 

 phogenetic material. This is true. 



Nevertheless, we may consider the complex association of 

 the cortical network with kinetosomes. The cortical net- 

 work, as has been shown, is a rigid structure in highly 

 evolved mature ciliates. On the contrary, kinetosomes may 

 multiply and increase in mimber as do other particles en- 

 dowed with genetic continuity. 



We know that something in the cortical structure orients 

 the kinetosomes and the kinetodesmas. What mav be the 



