PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 343 



stome. Lillie ('96) has recently found that Stentor may by shaking 

 be broken into fragments of all sizes, and that nucleated fragments 

 as small as ^V tne volume of the entire animal are still capable of 

 complete regeneration. All non-nucleated fragments perish. 



These studies of Nussbaum and Gruber formed a prelude to more 

 extended investigations in the same direction by Gruber, Balbiani, 

 Hofer, and especially Verworn Verworn ('88) proved that in Poly- 

 stomella, one of the Foraminifera, nucleated fragments are able to 



Fig. 159. Regeneration In the unicellular animal Stentor. [From GRUBER after BALBIANI.] 



A. Animal divided into three pieces, each containing a fragment of the nucleus. B. The three 

 fragments shortly afterward. C. The three fragments after twenty-four hours, each regenerated 

 to a perfect animal. 



repair the shell, while non-nucleated fragments lack this power. 

 Balbiani ('89) showed that although non-nucleated fragments of 

 Infusoria had no power of regeneration, they might nevertheless 

 continue to live and swim actively about for many days after the 

 operation, the contractile vacuole pulsating as usual. Hofer ('89), 

 experimenting on Amoeba, found that non-nucleated fragments might 

 live as long as fourteen days after the operation (Fig. 160). 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 



