METHOD OF CELL DIVISION IN MONIEZIA. 151 



duct after passing through the vitellarium and shell gland joins 

 the oviduct the point of union being known as the ootyp and 

 this latter duct Continues to the uterus. 



Cases of polyspermy frequently occur; that is, some eggs show 

 more than one male pronucleus. I have not observed the en- 

 trance of several spermatozoa into the same egg, but this is not 

 surprising since the entrance of a single spermatozoon is rarely 

 seen. In many proglottids some of the segmenting eggs ulti- 

 mately degenerate ; possibly they include the cases of polyspermy. 



In certain proglottids ova are found in the seminal receptacle, 

 sometimes in quite large numbers. As the seminal receptacle 

 is not ruptured in many of these cases it would seem that in 

 passing through the ootyp the eggs had crowded past the branch 

 of the oviduct leading to the uterus and forced their way through 

 the fertilization canal into the seminal receptacle. There they 

 degenerate. It is, of course, very probable that polyspermy 

 occurs here but so densely packed are the spermatozoa about 

 the egg that the process cannot be followed. 



For figures of the fertilization stages as well as for additional 

 figures of the maturation divisions the reader is referred to 

 Child's paper ('070). 



Child's account of the maturation divisions agrees in essentials 

 with my observations, and I shall, therefore, merely give a brief 

 resume of this stage of development. 



The entrance of the spermatozoon furnishes the stimulus for 

 the formation of the vitelline membrane and for the beginning 

 of the maturation divisions. The first polar body is usually 

 formed by the time the egg has entered the first loops of the 

 uterus and the second polar body follows soon after. The first 

 division requires more time than the second if the relative fre- 

 quency in which the two stages occur may be regarded as a 

 criterion. Many more first divisions occur in my material than 

 second. 



The characteristics of these divisions are large globular centro- 

 somes ring-shaped in section faint astral radiations, 1 and a 

 very long spindle on which small chromosomes are to be seen 



1 Child stated that he was unable to see asters but thought they probably occur. 

 I have succeeded in distinguishing faint radiations in numerous maturation stages. 



