394 



PRINCIPLES OF EMBRYOLOGY 



kinetosomes lie in rows, and along the side of each row is a thread, 

 the kinetodesma, the whole complex being known as a kinety (Fig. 18.5). 

 It can be shown both by experiment and observation that kinetics develop 

 only out of pre-existing parts of kineties and they therefore possess at 

 least one type of genetic continuity. 



These kineties are of undoubted morphogenetic importance. In fact 

 the structure of a ciliate, which may be quite complicated, is in the main 



Figure 18.5 



On the left, a drawing of Stentor: mac.n., the nodular macronudeus ; ph, 

 peristome band ; cv, contractile vacuole ; ap, the adoral zone, from which the 

 new peristome band originates in regeneration ;/^ foot; lbs and rhs left and 

 right sides of the ramifying zone, from which new kineties are formed. 

 (Modified from Weisz 1951.) On the right, diagram of a ciliate, showing 

 one kinety (composed of kinetodesma and kinetosomes) on the near side, 

 and a similar one seen by transparency on the far side. (After Faure-Fremiet 



1950.) 



a matter of local differentiation of the cuticular layer or ectoplasm, and 

 this can be shown to depend on the activities of the kineties. The evidence 

 for this comes largely from observation of the process by which a single 

 individual becomes reorganised into two at the time of ceU-division, and 

 from studies of the processes of regeneration of a whole individual from 

 fragments. In both cases it is clear that the kineties are reorganised first, 

 and only later produce the more obvious morphological structures such 

 as the gullet, flagellae, cirri, trichocysts, etc. The kineties associated with 

 these various organs do not, however, become fully determined, so as to 

 possess only one specific character; thus a kinety originally associated 



