56 Indications of a Central Zone of Development 



eration. But that this was not actually the case was 

 demonstrated by more careful observation by which it 

 was recognized that the completeness was only apparent, 

 for no part altogether lost was reproduced and no new 

 mouth was formed in the place of the old one which had 

 been removed. 29 



From this one could almost infer that some analogous 

 phenomenon is the effective cause whereby the organs of 

 the peristomal field, as soon as they are all formed in their 

 essential parts, become arranged in the posterior anuclear 

 half in about the same way as they would be arranged 

 after the completion of spontaneous division. 



Even if we admit a true and proper continuation of 

 development, we must yet bear in mind first that it is not 

 at all certain that this posterior half was completely de- 

 prived of macro- or micro-nuclear substance. For the 

 micro-nuclei sometimes attain the number of fifty- four or 

 sixty-six in Stentor coereleus, and it is always difficult to 

 see them, especially in individuals in process of sponta- 

 neous division. 30 



Secondly we must above all things get a clear under- 

 standing of what the remaining alive for a while of 

 anuclear fragments of adult individuals can signify, keep- 

 ing in view at the same time the absolute generative inca- 

 pacity of these fragments. They signify nothing else than 

 a posthumous persistence for a while of the special action 

 or series of actions, partly simultaneous, partly succes- 



29 Gruber: Uber Kiinstliche Teilung der Infusorien. Zweite 

 Mitteilung. Biol. Centralbl., Bd., V. No. 5; May i. P. 139140. 



80 H. P. Johnson : A Contribution to the Morphology and Biology 

 of the Stentors. Journal of Morphology, vol. VIII, no. 3. Boston, 

 U. S. A., Ginn, August 1893. P. 499- 



