478 Dr. A. Gruber on the 



divisions, although derived from quite different parts of the 

 body, are equally able to become developed into perfect 

 animals. There is, however, a difference in the mode of re- 

 generation of such different fragments, because in those 

 quadrants (if I may use the expression) which have retained 

 a portion of the peristomial circlet of cilia, the deficiencies 

 are made up by simple growth, whilst in the parts which show 

 no peristomial cilia the latter must be formed anew in the 

 wav above described. There is also no more difficulty in 

 dividing a Stentor into three pieces in such a manner as to 

 obtain the anterior and posterior ends and a median section 

 isolated from each other (fig. 4) ; this last is likewise able to 

 become perfectly regenerated in the same time as the other 

 fragments, although it has to form anew both the anterior and 

 the posterior extremities. 



Although these experiments distinctly prove the high rege- 

 nerative faculty of the Stentors, the following one does this still 

 more clearly : — A Stentor cceruleus, which I will indicate as 

 A, was divided transversely into two halves ; next day these 

 had grown into two perfect animals B and B' ; the anterior 

 end was now separated from B, and B' was again divided 

 transversely, when it appeared, after the lapse of twenty-four 

 hours, that B had again regenerated itself, and that the two 

 halves of B' had become developed into two perfect Infusoria, 

 C and C. B was again divided, but without result, as on 

 the next day it had perished ; while of the two divisional 

 pairs into which I had again divided C and C, only one 

 derived from C had perished, and the two halves of C had 

 again become regenerated into two small Stentors, D and D' ; 

 and, finally, I succeeded in obtaining artificially from D and D' 

 a generation E ; but these individuals had now become so 

 small that they had lost their vitality and soon perished. 1 

 had therefore succeeded in carrying out artificial division on 

 the same objects for five consecutive days in which regenera- 

 tion of the lost parts took place five times. 



Nussbaum has also demonstrated that artificially multiplied 

 Infusoria, under favourable conditions, are afterwards able to 

 divide further spontaneously, and I have observed the same 

 thing in my experiments. Thus, for example, on the 10th 

 December I had transversely divided nine Stentors and only 

 isolated the hinder extremities ; on the next day all the nine 

 had developed new, perfect peristomial areas with the ciliary 

 circlet and mouth ; on the 13th December one of these rege- 

 nerated animals showed the commencement of spontaneous 

 fission, and on the 15th the nine specimens had become fifteen, 

 which I kept alive until the end of the month. 





