24 MORPHOGENESIS IN CILIATES 



this phase, the production of trichocystosomes proceeds in 

 exactly the same way as in the tomite. 



The production of trichocysts continues until the second 

 division. During the divisions, the kinetosome produces 

 two trichocystosomes. Only the distal one produces tricho- 

 cysts. It seems that also some trichocystosomes may be 

 detached, are able to migrate, and are the origin of the 

 trichocysts which are scattered all over the surface. 



Here again, it is clear that the differentiation of kineto- 

 somes into trichocystosomes depends on the phase of the 

 life cycle and presumably on the properties of the cyto- 

 plasm. 



Foettingeria will provide another and more remarkable 

 example of differentiation. The tomite produces trichocysts 

 like other tomites. After liberation from the palintomic 

 cyst, the tomite encysts on a non-specific crustacean. When 

 the host is ingested by a coelenterate, the cycle will be com- 

 pleted, but the trophont, unlike the others, will not only 

 accumulate food. It will grow. The enlarged macronucleus 

 finally forms a complicated network. During the first 12 

 to 14 days, after an experimental infection, nothing re- 

 markable happens: the kinetosomes remain normal. But 

 after 2 weeks, these kinetosomes will multiply and produce 

 trichites. , These differ from trichocysts in that, whereas 

 trichocysts are tubular structures able to be protruded, 

 trichites are homogeneous organites devoid of this property. 



The multiple potencies of the kinetosomes thus express 

 themselves during the life cycle. The kinetosome is able 

 to divide and to produce cilia. In the tomite, it produces 

 a differentiated granule, the trichocystosome, which gives 

 rise to a trichocyst. In the 2-week-old trophont it produces 

 differentiated granules, the trichitosomes, which multiply 

 and produce trichites. The fate of the granule is controlled 

 not only by its position, but also by the phase of the life 

 cycle. 



