RELATION BETWEEN AMITOSIS AND MITOSIS. 1 47 



After passage of the eggs from ovary to uterus has occurred 

 several times the different stages are mingled together in great con- 

 fusion in the uterus for the uterus is now larger than in earlier stages 

 and the eggs move more freely through it with the contractions 

 of the body. In these proglottids particular stages are not con- 

 fined to particular regions of the uterus : early maturation and 

 later cleavage stages may occur side by side but even here the 

 earlier stages are more abundant in the lateral and the later in 

 the middle regions of the uterus. 



That portion of the oviduct which lies between the entrance of 

 the spermathecal duct and the uterus is highly convoluted and 

 possesses thick walls, but no portion of it functions as a shell- 

 gland. The egg passes into the uterus surrounded only by the 

 vitelline membrane and this often disappears during cleavage. 



Moreover, although a well developed vitellarium is present no 

 yolk-cells pass into the uterus with the egg. To all appearances, 

 the vitellarium undergoes degeneration in situ, though it is pos- 

 sible that yolk-cells may pass into the uterus in stages later than 

 those which I have observed, or it may be that the reserve sup- 

 plies of nutriment in the yolk-cells are altered by enzymes and 

 so pass into the uterus in fluid form where they undergo resorp- 

 tion by the embryos. 



It is very evident that the transference of the embryos of 

 Moniezia to the intermediate host must occur either within the 

 proglottid or in fluid since the absence of a shell or capsule of 

 any kind would exclude the possibility of exposure to the 

 atmosphere. 



V. Conclusion. 



Maturation and fertilization occur in Moniezia in a manner not 

 essentially different from that observed in other forms. Evidently 

 the earlier amitotic history of the germ-cells does not interfere in 

 any way with their properties as germ-cells. 



Moreover, although the embryonic development begins with 

 mitosis, at least in most cases, if not in all, this soon gives place 

 in large measure to amitosis, mitosis occurring only occasionally 

 in the larger nuclei in the more slowly dividing regions. Here 

 then, as in the development of the germ-cells, amitosis is appar- 



