90 MORPHOGENESIS IN CILIATES 



metabolism of the kinetosome. But in some flagellates, as 

 well as in some ciliates, the only product of the kinetosome 

 is a cilium. This again may be due either to environmental 

 differences or to differences of the constitution of the kineto- 

 some itself. Transplantations, if they are possible, should 

 help solve the problem. What we see, in fact, is that under 

 apparently precise and perfectly unknown conditions one 

 granule produces what we may consider an orientated and 

 orderly polymerization of some material or materials (pro- 

 teins, polysaccharides, lipids). 



Whatever the intimate cause of the polyvalency of kine- 

 tosomes may be, the polyvalency remains. The kinetosomes 

 themselves and their products are one mode of expression 

 of ciliate characters. And here is perhaps the main origi- 

 nality of ciliates. Most structures of highly differentiated 

 ciliates are rigid formations, unable to divide. But they 

 are able to undergo dedifferentiation, and apparently their 

 building blocks can be utilized again. The kinetosomes, 

 except when they are turned into trichocystosomes, main- 

 tain their primitive features. They remain able to divide, 

 to be organized in specific patterns together with other pro- 

 ductions of the ciliates. 



What is rigid in evolved ciliates is the sum of the kineto- 

 somes + kinetodesmas + cortical network which consti- 

 tute the specific pattern. Differentiation in a ciliate is an 

 organization. But the properties of the whole organism 

 are not necessarily the sum of the properties of the constitu- 

 ent parts. The ciliate as an organism remains totipotent, 

 able to divide and to be reorganized. It can do this because 

 differentiation does not affect the whole organism, but only 

 its cortex, and because the responsible self-reproducing 

 cytoplasmic units are not them.selves changed during the 

 process of organization. And so we are able to understand 

 why a cyclical dedifferentiation is necessary in highly 

 evolved non-cellular organisms. 



