22 Marj Blount. 



which are added to the germinal area. They are in such positions 

 as would make it possible for them to enter into the structure of 

 the embryo. Rlickert thinks tliat the cells containing mcrocyte 

 nuclei may soon degenerate, or if they play any part in the develop- 

 ment, it must be only subordinate. (Rlickert '99, p. 677). Upon 

 general principle, he is unwilling to admit that nuclei derived from 

 supernumerary spermatozoa enter into the structure of the embryo, 

 and so he finally leaves it an open question whether the merocytes 

 of late cleavage degenerate in the germ layers, or whether their nuclei 

 are not genetically related to merocyte nuclei of early cleavage but 

 are a new set derived from the cleavage nucleus (Rlickert, '99, p. 

 677). 



Ruckert's Explanation for the migration of the supernumerary 

 sperms. — Rlickert presents a theory for the cause of the migration 

 of the supernumerary sperm nuclei. He considers that the sperm 

 nucleus entering first, or the one lying nearest to the female pro- 

 nucleus, becomes the male pronucleus. With the copulation of the 

 pronuclei, the a^ntrosomes and asters of the male nucleus pass over 

 to the cleavage nucleus. The supernumerary sperm nuclei are re- 

 pelled from the cleavage nucleus and from each other by the in- 

 fluence of their astral rays. These fibers reach out from the nuclei 

 and when they touch each other, they respond to a stimulus some- 

 what like thigmotaxis — but in this case, the fibers touch others like 

 themselves instead of a firmer object. When the fibers thus come 

 in contact, the nuclei recoil. The cleavage nucleus being better 

 endowed, drives the other nuclei away from it. The succeeding 

 generations of cleavage nuclei are armed with the protective ap- 

 paratus ("Schutzvorrichtung"), their inheritance from the male 

 pronucleus, and as cleavage advances, there is therefore a progressive 

 combat between the cleavage nuclei and the supernumerary sperm 

 nuclei for the possession of the germinal area. The cleavage nuclei 

 are stronger and therefore triumph over the weaker, which are con- 

 tinually "driven to the wall." This behavior, Rlickert thinlvs, ac- 

 counts not only for the expulsion of the supernumerary nuclei 

 (merocyte nuclei) from the central area, but it explains the some- 

 what equal spacing of them around the periphery and in the deeper 

 parts. 



