I46 C. M. CHILD. 



observations certainly indicate, though they are not sufficient to 

 prove positively, that cleavage is indeterminate and exceedingly 

 irregular. 



My material thus far has not included stages of development 

 later than those shown in Plate VI. I hope in future, however, 

 to obtain later stages and to continue the study of the role played 

 by amitosis and mitosis in the later development. 



In Figs. 3 3-40 (PI. VII.) several single blastomeres and nuclei 

 from various stages of cleavage are figured as showing par- 

 ticularly clear and convincing cases of amitosis. 



IV. General Observations. 



In this section a few observations of general biological interest 

 though not connected with the chief purpose of the paper are 

 briefly given. As was pointed out in the first paper of this series 1 

 the eggs in those portions of the ovary nearest the opening of the 

 oviduct begin and complete their growth earlier than the others. 

 Proceeding from this region toward the tips of the ovarian fol- 

 licles, we find that oogenesis is slightly later at each successive 

 level. Thus the eggs nearest the oviduct are the earliest, while 

 those at the tips of the follicles are the latest to attain full growth. 



There can be no doubt that the passage of ova from the ovary 

 to the uterus is periodical and not of continual occurrence, for in 

 most proglottids in which embryos are present in the uterus and 

 immature eggs in the ovary, no eggs are found in the oviduct. 

 In such proglottids nothing later than late maturation stages or 

 cleavage stages is found in the uterus. Occasionally, however, 

 a proglottid is found with eggs in the oviduct, and such cases 

 show the entrance of the spermatozoa in those eggs in the ovi- 

 duct and usually earlier maturation stages in the eggs in the 

 lateral region of the uterus. 



The egg usually reaches the lateral portions of the uterus 

 before the appearance of the first maturation spindle. In the 

 uterus, maturation stages and early cleavage stages become more 

 or less mingled, although the maturation stages are usually more 

 abundant in the lateral portions of the uterus and the cleavage 

 stages in the middle portions. 



1 Child, C. M., Biol. Bull., XII., 2, 1907. 



