GENETIC CONTINUITY OF KINETIES 43 



If wc consider the rows x, y, z, we reach the same conclu- 

 sions. The conditions for thcii- maintenance are reaUzed 

 only in the median part of the tomite. 



The fact that the anterior sector of the kinety x will form 

 the rosette or mouth organ seems to show that some special 

 morphogenetical field is always located in the corresponding 

 region. Nevertheless, the hypothesis cannot be excluded 

 a priori that the kinetosomes and fibers of the row x possess 

 some special properties which are responsible for their re- 

 sponse. According to this hypothesis, the formation of the 

 rosette would be not the effect of a localized morphogeneti- 

 cal field, but the reflection of the properties of a specialized 

 kinety to conditions present everywhere. But it is difficult 

 to understand, if this hypothesis is admitted, why it is not 

 the kinety a: as a whole which is turned into a rosette. 



Nevertheless, this brings up the problem of the different 

 behavior of different kineties. A somatic ciliary row of 

 Gyinnodinioides and of other apostomes is endowed with 

 genetic continuity. A given somatic kinety of the proter 

 and of the opisthe is the anterior or the posterior part of the 

 parent's kinety. This is the type called "direct continuity 

 by elongation" by E. Chatton and A. Lwoff. The reproduc- 

 tion of X, y, z is of the same type, with the difference that 

 they are bipolar only before division, whereas in the resting 

 phase they are reduced to a short segment of five to twenty 

 kinetosomes, according to species. 



In Pericaryon cesticola y and z have only two kineto- 

 somes and X only one. What happens when the regression 

 reaches its limit, that is to say, when a ciliary row present 

 during one phase disappears during the following phase? 

 How is it regenerated? In Polyspira and Gymnodinioides, 

 the rows h and c disappear during the tomital and phoretic 

 phase and are absent in the trophont. Before and during 

 palintomy, the kinetosomes of a divide and form an anarchic 

 field, the kinetosomes of which are later oriented in two 

 lines h and c. 



