344 Behaviour of the Infusorian Micronucleus in Regeneration. 



have utterly failed to direct the division of the hind micronucleus, with the 

 result that one product has been carried to the very posterior end of the cell. 



These phenomena are to be compared with those exhibited by the micro- 

 nucleus of Paramecium. Normally lying in a notch in the side of the 

 meganucleus, the organella moves out, or is swept away, into the endoplasm 

 on occasions when the animal is starving or in depression. Here is shown 

 the same stereotyped position of the micronucleus, and the same occasional 

 failure of the forces concerned to maintain it. 



The experiments recorded above were performed at the Stazione Zoologica, 

 in Naples, during my tenure of the Cambridge University table there. To 

 the officials of the station I wish to express my thanks for many kindnesses. 



I am indebted as Coutts Trotter Student to the authorities of Trinity 

 College for permission to hold the studentship at Naples. 



LIST OF CITED LITERATURE. 

 Balbiani ('92). "Nouvelles recherches experimentales sur la merotomie des Infusoires 



cili6s," ' Ann. de Micrographie,' vol. 4, pp. 369, 449. 

 Calkins ('11). " Regeneration and Cell Division in Uronychia," 'Journ. Exp. Zoology,' 



vol. 10, p. 95. 



Johnson ('93). " A Contribution to the Morphology and Biology of the Stentors," 



' Journ. of Morphology,' vol. 8, p. 548, note. 

 Le Dantec ('97). "La regeneration du micronucleus chez quelques Infusoires cilies," 



'C.-R. Ac. Sci.,' vol. 125, p. 151. 

 Lewin ('11). "Nuclear Relations of Paramecium caudatum during the Asexual Period," 



' Cambridge Phil. Soc. Proc.,' vol. 16, p. 39. 

 Popoff ('09). " Experimented Zellstudien. — III," 'Arch. f. Zellforsch.,' vol. 4, p. 1. 

 Stevens ('03). "Further Studies on the Ciliate Infusoria, Licnophora and Boveria, 



' Arch. f. Prot.,' vol. 3, p. 1. 



