ASPECTS OF THE KINETOSOME 31 



structure, metabolic processes are dependent on active 

 substances, probably of relatively low molecular weight, 

 emanating from the nucleus." 



Is it possible to apply this conception to the kinetosome? 



If we consider one ciliate at a given phase of its cyc'le, we 

 see that the formation of all the trichocystosomes from 

 kinetosomes takes place simultaneously. This change is 

 therefore not the result of a random modification, but the 

 result of the interaction of the kinetosome with some spe- 

 cific substance. 



It is nevertheless a complicated process involving: 



a. The production by the kinetosome of a modified 

 granule. 



b. The production of a trichocyst or a trichite. 



As, in the tomite, all the daughter kinetosomes produce 

 trichocysts at once, two hypotheses must be considered: 



1. All the kinetosomes have undergone a normal equa- 

 tional division. But the environment being changed, the 

 interaction of the daughter kinetosome with these "con- 

 ditions" results in the formation of a trichocyst instead of 

 a cilium. This w^ould mean an induced modification of the 

 specific activity of the granule. The data concerning 

 adaptive enzymes, which have been so pertinently and care- 

 fully reviewed by J. Monod (1947), allow the hypothesis 

 that one substance could inhibit some enzymes, thus modi- 

 fying the nature of the end product of the activity of the 

 kinetosome. It is possible also to consider the hypothesis 

 that kinetosomes possess many enzymes and that, owing to 

 the availability of diverse substrates, one or the other of 

 these enzymes is able to function. 



2. The kinetosome has undergone an unequational divi- 

 sion. As all the daughter kinetosomes produce trichocysto- 

 somes, this cannot be the result of a random modification. 

 It can only be the result of the interaction of the mother 

 kinetosome with some specific substances, that is to say, 

 an induced modification. 



