Physiology and Biology of the Protozoa. 483 



das Wachstlium einzelHger Thiere," in the ' Biologische 

 Centralblatt ' (Band iii. p. 580), and at the end of the article 

 put forward the proposition " that the nucleus has no import- 

 ance in those functions of the cell-body which do not stand 

 directly in relation to reproduction." 



I said expressly all functions which do not stand in relation 

 to reproduction, and, as will appear hereafter, I had in this 

 judged quite correctly : a further vegetation and even an 

 increase in size is j^ossible, even without a nucleus^ under 

 certain circumstances^ hut a reproduction or regeneration (i. e. 

 anew production of parts of the body) cannot occur without the 

 intervention of the nucleus. 



Considerable difficulties lay in the way of the experiments 

 with Stentor, inasmuch as the necklace-like nucleus traverses 

 the whole body, and it is therefore difficult to separate a part 

 in such a way that it should contain no portion of the nucleus. 

 I first of all tried to cut away small portions of the anterior 

 part of the body, and I succeeded frequently in avoiding any 

 injury to the nucleus in so doing (fig. 8 a). After isolating 

 them I found such small pieces on the following day tolerably 

 perfect in form ; I stained them with picrocarmine, when it 

 appeared that they actually contained no nuclear constituent 

 (fig. 8 b) , and I thought I might now conclude from this that 

 a regeneration might occur even without the presence of a 

 nucleus. I was also led to the same conclusion at first by another 

 experiment : — Starting from the fact that the necklace-like 

 nucleus of the Stentors fuses during fission into a bean- 

 shaped mass, I selected individuals which just showcd^the 

 commencement of division, i. e. in which the middle of the 

 body was just beginning to show a new peristome (fig. 9) ; 

 in one such individual I succeeded in making a transverse 

 section immediately in front of the foundation of the peri- 

 stome in such a way that the greater part of the mass of the 

 nucleus was caused to escape. The two portions were iso- 

 lated, and on the following day both had become quite perfect 

 animals. When stained on the slide * it now appeared that 

 one of these two Stentors actually possessed no trace of a 

 nucleus, while the other contained only a small residue of it. 

 In this case also therefore regeneration had apparently 

 occurred without the influence of the nucleus. On more 

 particular investigation, however, both this and the former 



* Steutors may \evj easily be stained on the slide, as, wlien flooded 

 with ahsohite alcohol, they usually remain firmly attached to the glass. 

 In this Infusorian particularly the nucleus takes up picrocarmine with 

 extraordinary avidity, and is always stained dark red before the cyto- 

 plasm begins to acquire colour, 



