136 GERM-CELL CYCLE IN ANIMALS 



CESTODA. Child concluded (1904) from a study 

 of the cestode, Moniezia expansa, that this method 

 of cell division occurs in the antecedents of both 

 the eggs and the spermatozoa. This writer has 

 published a series of papers upon this subject using 

 Moniezia expansa and Moniezia planissima for his 

 material (1904, 1906, 1907, 1910, 1911), and his 

 principal conclusion is that in these species the 

 division of the cells destined to become eggs and 

 spermatozoa is predominantly amitotic. Mitotic 

 division also occurs but comparatively rarely. Cells 

 which have divided amitotically then divide mitoti- 

 cally during maturation and form typical ova. 



The nature of the nuclear division in the cestodes 

 was later investigated by Richards (1909, 1911) who 

 studied the female sex organs of the same species 

 employed by Child as well as material obtained from 

 Toenia serrata. Richards finds that mitosis unques- 

 tionably occurs in the young germ cells but was 

 unable to demonstrate amitosis. Richards claims 

 that amitosis cannot be demonstrated except by the 

 observation of the process in the living material and 

 the subsequent study of this material by cytolog- 

 ical methods. Child (1911) agrees with Richards 

 that amitosis cannot be demonstrated in fixed 

 material but nevertheless concludes after an examina- 

 tion of Richards' preparations "that direct division 

 plays an important part in the developmental cycle 

 of Moniezia, in the germ cells as well as in the soma " 

 (Child, 1911, p. 295). 



Finally Harman (1913) was unable to find any 



