RELATION BETWEEN AMITOSIS AND MITOSIS. I4I 



The second polar body is, as is usual, smaller than the first 

 (Fig. 11, PI. III.) both as regards nucleus and cytoplasm. Divi- 

 sion has not been observed in either polar body, though in one 

 case what appeared to be an abnormal or abortive mitosis was 

 seen in the first polar body. 



Fig. 11 (PI. III.) shows the reconstitution of the female pronu- 

 cleus by the fusion of vesicles which doubtless arise from differ- 

 ent chromosomes. 



II. Fertilization. 



The spermatheca opens into the oviduct at a point near the 

 junction of the latter with the ovary. At the time when the eggs 

 pass into the oviduct the spermatheca is distended with great 

 numbers of spermatozoa a few of which are found in the narrow 

 duct connecting spermatheca and oviduct. The spermatozoon 

 meets the egg as it passes along the oviduct past the opening of 

 the spermathecal duct. 



Apparently the passage of the eggs through from the ovary to 

 the uterus is periodical for among the large numbers of proglot- 

 tids sectioned which contained cleavage-stages in the uterus and 

 fully grown unfertilized eggs in the ovary only a very few show 

 eggs in the oviduct. Among these, however, it has been possible 

 to find a few cases showing the entrance of the sperm. 



Fig. 1 (PI. II.) shows the clearest case observed of this stage. 

 It will be recalled x that the fully developed spermatozoon is 

 greatly elongated and filiform without any trace of a visibly dif- 

 ferentiated head-region, except that its diameter is slightly greater 

 anteriorly than posteriorly. 



In all cases where the spermatozoon was found on the egg it 

 was in contact with the surface over more or less of its length, as 

 if adhering to it. Frequently it was wound several times about 

 the egg, the remaining portion hanging free in the oviduct or ex- 

 tending into the spermathecal duct. 



In Fig. 1 the course of the spermatozoon body over the sur- 

 face of the egg is indicated but only a fraction of the length of 

 the spermatozoon is shown. The figure scarcely exaggerates the 

 clearness of the section itself. That portion of the sperm which 



1 Child, Biol. Bull., XII, 4, 1907. 



