390 



TRANSACTIONS OF THE 



[dec. 13, 



repeated research, I have been unable to distinguish a definite 

 centrosome at the center of the aster. The center appears granu- 

 lar, but certainh' contains no such definite bod}' as is seen later. 

 The sperm-aster certainly grows by transformation of the cyto- 

 plasmic network of the egg into fibers. Whether it all arises 

 from this source it is impossible to state. 



Fig. ^ 



The chromosomes now divide and pass to the two poles, and 

 the first polar body is formed in the usual manner. The inner 

 portion of the spindle resolves itself rapidly into the C3'toplasmic 

 network, and the two centrosomes left at the inner pole move 

 apart and are seen to be connected by a delicate spindle. This 

 increases in size and distinctness, and polar radiations appear 

 as the centrosomes become farther removed from each other. 

 This second polar spindle revolves as it grows, assuming the 

 position occupied by the first, and the chromosomes arrange 

 themselves meanwhile on its equator. 



The fully formed second polar spindle (Fig. 4) is very similar 

 to the first in appearance, but smaller, and possesses much 

 smaller polar radiations. It usualh' shows one ce'ntrosome at 

 each pole, though in some cases two appear at the inner pole in 

 late equatorial plate stages. Whether two occur at the outer 

 pole also it has been impossible to ascertain. The chromo- 

 somes now divide and the second polar body is formed, being 

 somewhat smaller than the first. A division of the first polar 

 body was never seen to occur. 



In Fig. 4, to the right of the spindle, is seen a sperm-head 

 with a single aster containing a centrosome. At about this 

 stage the centrosome of the "male " aster divides. One of the 

 resulting centrosomes remains near the sperm-head, and the 

 other moves some distance from it. The two are connected by 



