DERI VED ORG A NIZA TION 



123 



which may turn out to be homologous with one or more of these 

 structures. Endobasal bodies, however, are known in micronuclei 

 of a few T types (e. g., Uroleptus mobilis, Oxytricha fallax) and in some 

 macro nuclei (e. g., Chilodon cucullw, Fig. 30, p. 62). On the other 

 hand, certain special types of cytoplasmic kinetic elements such as 

 myonemes, motorium, and conductile fibers, are characteristic of 

 the ciliates, some of which become highly complicated coordinated 

 neuromotor elements. 



v ',1 :.-^..~~' J — '<•*■ 



D 



!■■}; 



'■,'■ i 



X 



fflSfes 





'.•■';- : /,. ;: ^.?J 'l/'fc-' 



7^ 



Fig. 68. — Actinosphaerium eichhornii; origin of centrosome from nucleus. 

 (After Hertwig.) 



The most widely distributed of the kinetic elements are the basal 

 granules of the cilia, which are situated in the contractile zone of 

 the cortex and form a part of the silver line system (see p. 80). 

 The exact nature of these extremely minute bodies is unknown and 

 their origin or renewal is purely hypothetical. Collin (1909) and 

 Entz (1909) record some observations which suggest their derivation 

 from nuclei (Entz) or at least some connection with them (Collin). 

 A single basal body gives rise to a single cilium (Fig. 69) but groups 

 of them are found at the bases of the more complicated membranes, 



