158 



FERTILIZATION OF THE OVO'M 



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. 1^8. — Fertilization of the egg of the parasitic annelid Myzostoma. [WHEELER.] 

 A. Soon after entrance of tlie spermatozoon ; the sperm-nucleus at J ; at ? 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 the jr/t'r;«-amphiaster. 



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

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

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



