32 MORPHOGENESIS IN CILIATES 



During the trophic phase of Polyspira, trichocystosomes 

 are formed and produce trichocysts whereas "normal" kine- 

 tosomes continue to produce cilia. Of course, there are 

 considerable differences between a normal kinetosome and 

 a trichocystosome. The first is close to the kinetodesma 

 and, so far as we know, connected to it by a fiber. The 

 second is far away (relatively) from the kinetodesma and 

 not directly connected with it. It is therefore possible 

 either (a) that the substance controlling the production of 

 cilia is located near the kinetodesma; or (b) that the at- 

 tachment to the kinetodesma is responsible for some orien- 

 tation of an unknown material and controls the formation 

 of cilia. The choice is difficult between alternatives a and 

 b. It is also difficult between hypotheses 1 and 2. 



But the one conclusion remains: the metabolism of the 

 kinetosome and of its daughter particles is controlled by the 

 environment. Thus one ''plasmagene'^ may possess many 

 prospective potencies and turn out different organelles ac- 

 cording to its position and to the phase of the life cycle. 



The study of apostomatous ciliates has thus led to the 

 morphological demonstration of self-reproducing cytoplas- 

 mic units. We are able to conclude not only that specific 

 cytoplasmic particles should exist, but also that they do 

 exist. 



The study of their behavior during the life cycle of the 

 ciliates furnishes an illustration of the conceptions schema- 

 tized by Weiss under the name ''molecular ecology/' which 

 thus receives the support of visible allies. 



The question of the equivalence of all kinetosomes will 

 be discussed in Chapter 6. Let us admit, for the time being, 

 that all kinetosomes are essentially equivalent, but are or- 

 ganized in different systems and structures, according to 

 their position in the ciliate and the phase of the life cycle. 

 And as these differences are observed in a single ciliate, the 

 hypothesis of a change in the genome being responsible for 



