THE CENTROSOME IN EERTILIZAriOX 



209 



of the middle-piece is likewise not marked off from the tail, yet as we 

 have seen (p. 165) the centrosome passes into this part of the sperma- 

 tozoon. Kostanecki's later examination of the fertilization of the 



Fig. 104. — Fertilization of the &gg of the parasitic annelid, Myzostoma. [WUKKLHk.j 

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

 vesicle; at c the double centrosome. B. First polar body formins; at 9 ; ;/. tlic cast-out nucle- 

 olus or germinal spot. C. The polar bodies formed {p.b.)\ germ-nuclei of equal size; at <: the 

 centrosomes. D. Approach of the germ-nuclei ; the amphiaster formed, 



same animal ('98), while inconclusive on the main point, loaves little 

 doubt that Wheeler's evidence was equally so ; for he has on the one 

 hand shown that the sperm-nucleus is often accompanied by a sperm- 



