CYTOLOGY OF SACCHAROMYCES CERVICL WITH 

 ESPECIAL REFERENCE TO NUCLEAR DIVISION. 



J. McA. KATER. 

 ST. Louis UNIVERSITY SCHOOL OF MEDICINE. 



For some years following the discovery of cell division it was 

 thought that direct division was responsible for the duplication 

 of the nucleus, and even after the discovery of indirect division 

 the former was still considered to be the usual method and 

 mitosis was held to be a peculiar and infrequent phenomenon. 

 Some held that the two processes were related and that mitosis 

 was derived from the simpler and more primitive one, amitosis. 

 However, as the investigation of this problem was continued 

 evidence was gradually accumulated to show that mitosis is the 

 usual if not universal method of cell division in higher animals 

 and plants, and that amitosis is not a reproductive phenomenon 

 at all, but has for its function the increase of nuclear surface in 

 relation to volume and is rarely, if ever, followed by cytoplasmic 

 division. This conception was well expressed by Conklin (1917) 

 in the following passage, "Mitosis and amitosis are fundamentally 

 unlike. Mitosis is the one and only method of bringing about 

 equal division and distribution of the chromatic material of the 

 nucleus. Amitosis is not a genuine divisional phenomenon at 

 all, but merely a means of increasing the nuclear surface and of 

 distributing nuclear material throughout the cell, comparable to 

 nucleur lobulation, fragmentation or distribution. These two 

 processes are not equivalent or even comparable, nor may one 

 of them be converted into the other." Although this view is 

 not universally held it is very generally accepted by cytologists 

 at the present time. 



The study of cell reproduction is much more difficult in 

 Protozoa than in higher forms, as many of the types of intra- 

 nuclear division have a superficial resemblance, to amitosis. 

 Minchin (1912) actually accredits the description of direct 

 division in a number of protozoa, although he admits that some 



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