324 Elliot R. Downing, The Ovogenesis of Hydra. 



Plate 12. 



Fig. 11, An egg of //. dioceia, about half grown, lying at the 

 margin of an ovary. 



Fig. 12. Margin of the egg of //. dioceia. 750:1. Showing the 

 collapse of the nucleus and formation of the coarser liuin net in the early 

 stages of the maturation phenomena. 



Fig, 13. Margin of the egg of //, dioceia. 750: 1. The spireme 

 stage in the formation of the first polar spindle. 



Fig. 14. //. dioecia. 750 : 1, Polar view of the first polar spindle 

 in anaphase. 



Fig. 15. The chromosomes of the preceding figure enlarged, showing 

 the component chromomeres. 



Fig. 16, H. dicjecia. 750 : 1, Side view of a first polar spindle. 



Fig, 17, //. dioecia. 750:1. Late anaphase of the first polar 

 spindle, polar view. 



Fig. 18, H. dioecia. 750: 1. The first polar body has been given 

 off into the space between three adjacent eggs. The nucleus of the 

 egg shows the coarse net; that of the polar body is degenerating. Com- 

 pare the size and structure of the egg nucleus with the nucleus of 

 Fig. 19. 



Fig. 19. Margin of an egg of //. dioceia. 750 : 1, The first polar 

 body shows between the margins of two adjacent eggs. The nucleus of 

 the egg increases in size very materially in the rest period between the 

 first and second polar spindles. 



Fig. 20, B. dioecia. 750 : 1. Margin of the egg showing the 

 nucleus in the spireme stage of the prophase preparatory to the formation 

 of the second polar spindle. 



Fig, 21. The nucleus of Fig. 20, enlarged. 



Fig. 22, //. dioecia. 750 : 1. Side view of second polar spindle in 

 anaphase. 



Fig. 23. H. dioeein. 750: 1, Side view of a second polar spindle 

 as usually seen, obscured by chromatin discharged from the nucleus during 

 the collapse which precedes the active division. 



Fig. 24. H. fusca. 1200: 1, Margin of an egg showing the 

 male pronucleus and the craterlike cavity through which the sperm 

 entered. 



Fig. 25, The next section to Fig, 24, showing the female pro- 

 nucleus. 



