The maturation and fertilization of the egg of Cerebratuliis. 447 



Other cases they may separate widely from each other as well as 

 from the sperm-nucleus. They are sometimes found on that side of 

 the sperm-nucleus which lies farthest from the polar bodies and from 

 the egg-nucleus (Figs. 23, 24). 



When the sperm-asters separate widely from the sperm-nucleus 

 there is no indication of any direct communication between the 

 fibres of the asters and the nucleus itself. The sperm-nucleus, 

 nevertheless, moves towards the egg-nuleus as rapidly as when 

 in contact with the asters. It seems certain, therefore, that 

 its movement is practically independent of any mechanical influence 

 of the asters. It certainly is in such eggs as those of Ascaris, of 

 Myzostoma (17, 32) and others in which the sperm-asters do not 

 appear until the germ- nuclei are close together, and in Pleurophyllidia 

 (18) where the sperm-asters form, but are lost at a very early stage. 

 KosTANECKi & WiERZEjSKi (15), OU the Other hand, consider that in 

 Physa there is always a direct connection by means of fibres between 

 the nucleus of the spermatozoon and its amphiaster even when they 

 are widely separated ^). In Cerehratulus when the asters do not lie 

 too far from the sperm-nucleus, some of their fibres may be followed 

 until they come almost into contact with it, but when they are more 

 widely removed from the nucleus this connection is entirely lost 

 although it may be resumed later. 



The final result is the same whether, after the early division of 

 the sperm-aster, the two resulting asters remain connected by a 

 semblance of a spindle or whether they separate ; whether they remain 

 near the sperm-nucleus or are far removed. For in every instance 

 we reach a stage in which the two asters and the two germ-nuclei 

 lie near together in the center of the egg, and when the asters have 

 increased so enormously in size that their fibres extend throughout 

 nearly the whole cell (Figs. 23—27). Figures 10, 12, 25 and 26 

 represent successive stages in the development of these asters. In 

 Fig. 10 the centrosome has divided, but the aster has not. In Fig. 12 

 the aster also has divided and there is a trace of a spindle between 



1) „Die Lage Veränderungen, welche der Kopf (Kern) des Samen- 

 fadens durchmacht, sind unserer Auffassung nach rein passiv und dürften 

 sich aus der Annahme erklären, dass der Zusammenhang zwischen dem 

 Spermakopf und der aus dem Verbindungsstück hervorgegangenen 

 Strahlung niemals aufgehoben wurde , die Strahlen vielmehr trotz der 

 Dehnung in Folge der Entfernung der Strahlenfigur mit dem Kopfe im 

 organischen Zusammenhange geblieben sind und denselben sodann dem 

 Strahlencentrum wieder nähern" (p. 351). 



