I 5 8 



FERTILIZATION OF THE OVUM 



on double-fertilized eggs, on imperfect method, on a misinterpreta- 

 tion of the double centrosomes of the cleavage-spindle, yet they still 

 remain an inexplicable anomaly of scientific literature. 



Fig. 78. Fertilization of the egg of the parasitic annelid Myzostoma. [WHEELER.] 

 A. Soon after entrance of the spermatozoon; the sperm-nucleus at tf ; at 9 the germinal 

 vesicle ; at c the double egg-centrosome. B. First polar body forming at $ ; n, the cast-out nucle- 

 olus or germinal spot. C The polar bodies formed (p.b.) ; germ-nuclei of equal size ; at c the 

 persistent egg-centrosomes. D. Approach of the germ-nuclei ; the egg-amphiaster formed. In 

 all other known cases this amphiaster is derived from 



Serious doubt has also been thrown on Conklin's conclusions by 

 subsequent research. Kostanecki and Wierzcjski ('96) have recently 

 made a very thorough study, by means of serial sections, of the fertil- 



