482 Dr. A. Gruber on the 



into irregular fragments, which then gradually become 

 regenerated into perfect animals ; we find the same thing in 

 Infusoria {Ojxdina) ; and, finally, a worm (e. g. Nais) may be 

 cut up artificially into pieces which are able to replace the 

 lost parts ; and the Infusoria, as already shown, possess the 

 same faculty. The only difference is that in the regeneration 

 of the Metazoa the cells perceptibly perform what in the Pro- 

 tozoa is the function of the elementary parts. 



The Signijicance of the Nucleus in Regeneration. 



When once the general fact of the regenerative faculty was 

 established, the next point was to ascertain the behaviour of 

 the nucleus in regeneration, and its influence, if any, thereupon. 

 In the above-mentioned experiments of the botanists upon 

 the multinucleate cells of Vaucheria it had been already pretty 

 certainly demonstrated that in artificial division large uuclei- 

 ferous portions continue capable of living, while small ones 

 without a nucleus perish ; nevertheless it could still be objected 

 that perhaps the smallness of the fragment might cause the 

 want of vitality. The following experiment of Nussbaum's 

 is more conclusive as to the indispensability of the nucleus in 

 regeneration : — " In one instance an Oxytrichine was divided 

 in the direction of its length. On microscopic examination it 

 appeared that all the four nuclei had escaped by the cut 

 surfaces. The fragments were enucleate. The smaller one 

 moved for three hours by the retained ciliary action. The 

 larger fragment lived on until the following day, but had not 

 resumed the Oxytrichine form, as had been the case in all the 

 numerous other experiments in nucleiferous fragments. It 

 moved about in the fluid in the form of a short-tailed sphere. 

 On the second day after the artificial division this piece also 

 had perished." " It would therefore appear," says Nuss- 

 baum, " that for the preservation of the formative energy of 

 a cell the nucleus is indispensable." Although he did not 

 choose to state this proposition with perfect certainty, this was 

 probably due to the fact that he could only appeal to a single 

 experiment, in which perhaps inappreciable accidents might 

 have come into play ; and therefore I tried whether with 

 Stentor any further support for the above-mentioned opinion 

 could be obtained. I was myself not a priori convinced of 

 it, for I had frequently had occasion to observe apparently 

 unaltered existence in Protozoa which had lost their nucleus ; 

 and I have already described my own and some other obser- 

 vations upon this point under the title of "Ueber dicEinfliiss- 

 losigkeit des Kerns auf die Bewegung, die Eruahrung und 



