324 ROBERT CHAMBERS. 



By means of the microdissection needle it is possible to show, at 

 the stage shown in Fig. 6-d, that the membrane of the germinal 

 vesicle no longer exists. By careful manipulation it was possible 

 to push the cytoplasmic granules into the nuclear area. A slight 

 rapid movement of the needle, however, was sufficient to give rise 

 to disintegrative processes similar to those on tearing an intact 

 germinal vesicle. In the normal maturation process the mingling 

 of the nuclear sap with the cytoplasm is very gradual, being com- 

 pleted in the case recorded not under ten minutes. It is this grad- 

 ual mixing which apparently prevents disintegration. 



Morgan ('93) and Mathews (Wilson and Mathews, '95) found 

 that maturation was accelerated by shaking starfish eggs shortly 

 after they were placed in sea water. They concluded that the 

 shaking ruptured the membrane of the germinal vesicle and so 

 allowed the nuclear material to mix more quickly with the cyto- 

 plasm. I have repeatedly tried to intermix cytoplasm and nuclear 

 material by rupturing the nuclear membrane of the starfish egg 

 with the needle, but in every case I get an explosive disintegration 

 of the cytoplasm. The ruptured nuclear membrane which Mathews 

 (W. and M., '95) and Marcus ('07) describe in fixed and stained 

 immature eggs which had been violently shaken is possibly the 

 membrane of the sphere which I found to persist after injury to 

 the germinal vesicle (see page 321). It is more likely that the 

 shaking which accelerates processes within the egg leads to the 

 normal gradual dissolution of the nuclear membrane and the subse- 

 quent diffusion of the nuclear material throughout the egg. I have 

 been able to do this occasionally with the needle. An intact ger- 

 minal vesicle which to all appearances should take fifteen to 

 twenty minutes to go into dissolution will often immediately ex- 

 hibit a wrinkled outline on being gently agitated with the needle. 

 Then follows the gradual fading from view of its outline with the 

 subsequent changes as shown in Fig. 6. 



The intact germinal vesicle may be brought into the sea water by 

 tearing away the surrounding cytoplasm. During the process the 

 nucleolus fades from view. The slightest tearing of the nuclear 

 surface then causes the entire liquid vesicle to disappear in the 

 water. If, however, the nucleus be left alone, it shrinks for a 



