RELATION BETWEEN AMITOSIS AND MITOSIS. I J J 



the surrounding cytoplasm, and so do not attain a condition in 

 which the cyclical processes characteristic of mitosis can occur. 

 It is not possible to determine the nutritive conditions with any 

 certainty at this stage. It is very evident in the later stages, 

 however, that those regions of the egg where the nuclei are 

 smallest and amitosis is most frequent are regions from which the 

 yolk is absent (Child, 'oyd, Figs. 27, 29, 30, 31). In the yolk- 

 bearing regions the nuclei divide much less frequently and more 

 often mitotically than in other regions. These facts point in the 

 same direction as those already cited with respect to other stages. 



In the somatic structures of the proglottid, mitosis has never 

 been observed except in the lateral regions of the proglottid and 

 very rarely there. When mitosis has been observed in the de- 

 velopment of the genital ducts it was usually at or near the periph- 

 ery of the proliferating region, in one of the cells which was evi- 

 dently less intimately involved in the proliferation than those 

 nearer the middle. These facts are in line with the preceding. 

 Moreover the somatic cells usually possess only a very small 

 amount of undifferentiated cytoplasm and this may be a factor in 

 determining the physiological condition of the nuclei and so the 

 form of division. 



It would appear then that the facts concerning occurrence and 

 relative frequency of amitosis and mitosis in Moniezia, as well as 

 in other forms, do not conflict with the suggestions made by way 

 of interpretation. There can I think be little doubt that the two 

 forms of division correspond to different physiological conditions 

 in the nucleus. Judging from the visible phenomena, it also 

 seems probable that mitosis is associated with cyclical, and ami- 

 tosis with acyclical processes. The questions as to the availability 

 of nutritive material and "equilibrium" are more obscure and 

 complex, for they concern not merely the presence or absence 

 of nutritive material outside of the cell, but, and probably chiefly, 

 its availability within the cell and for the nucleus. Various fac- 

 tors, such as quantity and quality of cytoplasm, size, form, and 

 condition of nucleus, etc., may conceivably play a part in deter- 

 mining the physiological conditions in the cell. Moreover, we 

 know little regarding the nature of nuclear equilibrium. I have 

 used the term merely with reference to a condition in which 

 cyclical processes with periodical reversals occur. 



