50 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.?9 
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.®° 
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- 
29Gruber: Uber Kiinstliche Teilung der Infusorien. Zweite 
Mitteilung. Biol. Centralbl., Bd., V. No. 5; May 1. P. 139—190. 
°°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. 
