PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 249 



clear fragment were smaller, the regeneration proceeded more slowly. 

 If no nuclear substance were present, no regeneration took place, 

 though the wound closed and the fragment lived for a considerable 

 time. The only exception but it is a very significant one was the 

 case of individuals in which the process of normal fission had begun ; 

 in these a non-nucleated fragment in which the formation of a new 

 peristome had already been initiated healed the wound and com- 

 pleted the formation of the peristome. Lillie ('96) has recently 

 found that Stentor may by 

 shaking be broken into frag- 

 ments of all sizes, and that 

 nucleated fragments as small 

 as gy the volume of the entire 

 animal are still capable of 

 complete regeneration. All 

 non-nucleated fragments per- 

 ish. 



These studies of Nussbaum 

 and Gruber formed a prelude 

 to more extended investiga- 

 tions in the same direction 

 by Gruber, Balbiani, Hofer, 

 and especially Verworn. 

 Verworn ('88) proved that 

 in Polystomella, one of the 

 Foraminifera, nucleated frag- 

 ments are able to repair the 

 shell, while non-nucleated 

 fragments lack this power. 

 Balbiani ('89) showed that 

 although non-nucleated frag- 

 ments of infusoria had no 

 power of regeneration, they might nevertheless continue to live and 

 swim actively about for many days after the operation, the con- 

 tractile vacuole pulsating as usual. Hofer ('89), experimenting on 

 Amceba, found that non-nucleated fragments might live as long 

 as fourteen days after the operation (Fig. 113). Their movements 

 continued, but were somewhat modified, and little by little ceased, but 

 the pulsations of the contractile vacuole were but slightly affected ; 

 they lost more or less completely the capacity to digest food, and 

 the power of adhering to the substratum. Nearly at the same time 

 Verworn ('89) published the results of an extended comparative 

 investigation of various Protozoa that placed the whole matter in 

 a very clear light. His experiments, while fully confirming the 



Fig. in. Stylonychia, and enucleated frag- 

 ments. [VERWORN.] 



At the left an entire animal, showing planes of 

 section. The middle-piece, containing two nuclei, 

 regenerates a perfect animal. The enucleated pieces, 

 shown at the right, swim about for a time, but finally 

 perish. 



