MUSEUM OF COMPARATIVE ZOOLOGY. 157 



Zellenvermehrung fiihren kanny When, however, both mitosis and 

 amitosis occur in the same tissue, he considers it probable that only the 

 former is the normal method of regeneration and of growth. 



The brief papers by Lowit, Verson, and Frenzel are replies to Ziegler's 

 ('91) recent article on amitosis, and contain little that is new. Verson 

 describes briefly the early stages in the spermatogenesis of the silkworm 

 (Bomhyx viori). He states that the spermatocytes originate from a 

 single large nucleus (" Riesenkern "), wliich divides repeatedly and 

 unequally by amitosis. The small daughter nuclei thus produced divide 

 by mitosis, and at length form the spermatocytes. Frenzel adduces 

 instances of amitosis in the intestinal epithelium of Crustacea and 

 Insects which do not fall within Ziegler's generalizations. 



Vom Rath's paper is a valuabla contribution to our scanty knowledge 

 of the occurrence of amitosis in spermatogenesis. He shows very con- 

 clusively that, in the testis of the crayfish, amitosis does not occur in 

 the generations of sperm-forming cells, but only in abortive nuclei 

 (" Randkerne "), which soon degenerate into an amorphous mass. If 

 such a fate could be established for all amitotically dividing nuclei in 

 the testes of animals, it would be much easier to form a logical estimate 

 of amitosis. 



