Physiology and Biology of the Protozoa. 485 



day, however, this piece had become regenerated, and on the 

 application of reagents it proved to be nucleated. Further, I 

 cut a Stentor, in the manner above described, into four pieces 

 (fig. 3) ; next day three of these pieces (A, B, C) were com- 

 pletely regenerated, one of them (D) not so, and this last 

 when stained proved to be non-nucleate, while the three others 

 had retained portions of the nucleus. The non-nucleate 

 piece, which was incapable of regeneration, was not at all 

 smaller than the others and less endowed with vitality on 

 account of smaller dimensions ; but all tlie four portions were 

 of about the same size, and the non-nucleate piece was even 

 of much larger dimensions than many parts separated in 

 other experiments which were very well regenerated *. 



The following experiment is still more conclusive as to the 

 importance of the nucleus in regeneration. If we cut away 

 the posterior extremities from a considerable number of 

 Stentors and isolate these separated parts, which therefore 

 retain no constituents of the peristome, we find them next day 

 in diiFerent states — some of them have become regenerated 

 into perfect Stentors with a new peristome, mouth, and oeso- 

 phagus ; in others the regeneration is in progress but not yet 

 quite completed ; and, lastly, in a third portion we only find 

 that the wound has closed up, the animals swim about like 

 the rest, but no trace of regeneration is exhibited. When 

 stained on the slide it is seen that the perfectly regenerated 

 pieces contain a normal necklace-like nucleus ; that those in 

 which the restoration is delayed have only retained a small 

 fragment of nucleus ; and that those which prove tc^ be 

 incapable of regeneration are quite destitute of nucleus. I 

 have frequently kept such non-nucleate pieces alive for 

 several days ; but they always perished without the occurrence 

 of any new-formations. 



I have also undertaken similar experiments with some other 

 Infusoria, but without further results, as they were all less 

 fitted for the purpose than Stento?: On the other hand, I 

 succeeded with Amoeba proteus in obtaining perfectly good 

 results. As is well known. Amoeba 2^roteus has only a single, 

 tolerably large nucleus j, and for this reason it is not difficult 

 to divide into a nucleate and a non-nucleate half (fig. 12). If 

 the section be made successfully and the two portions isolated, 

 we see that one of them continues without disturbance to 

 push forward and retract its pseudopodia (A), in short it has 

 undergone no change in its habit ; while in the other portion 



* I may mention tliat 1 several times repeated this and the following 

 experiment in order to insure myself against possible accidents, 

 t Gruber, " Studieu uLer Amoben, ' in Zeitschr. f. wiss. Zool. xli. 



