PLATE 6 



EXPLANATION OF FIGURES 



Hydractinia echinata 



47 Early fertilization stage in which the sperm has entered near the female 

 germ-nucleus. X 2625. 



48 Later fertilization stage showing the male germ nucleus somewhat ex- 

 panded. X 2625 



49 Fertilization stage in which the sperm head has entered the female germ- 

 nucleus before expanding, the chromosomes of the egg nucleus being already 

 formed. X 2625. 



50 Fertilization stage in which the two germ nuclei are of more nearly equal 

 size before union. X 2625. 



Eudendrium ramosum^ 



51 Gonophore containing an egg showing the position of the nucleus at the 

 inner end. X 75 



52 Same nucleus much enlarged, growth period. X 2625. 



53 Nucleus ready for maturation, showing the chromosomes forming. 

 X 2625. 



' All Eudendrium sections are of material fixed with sublimate acetic. 



246 



