442 BULLETIN OF THE 



While the phenomena of fecundation are, with slight modifications, 

 the same in all cases studied, the process of maturation is subject, in 

 his opinion, to greater variation. The simplest method of producing an 

 " egg nucleus " from the germinativ6 vesicle is by a uniform distribu- 

 tion of nuclear substance in the nuclear fluid, and then by a solution of 

 the nuclear membrane, such as appears to take place in conifers accord- 

 ing to Strasburger. With animal eggs, however, the process is more 

 complicated, and there are three methods to consider, of which the 

 simplest is that furnished by Toxopneustes, where the germinative 

 dot persists as " egg nucleus." With the leeches this is modified by 

 the intercalation of the accessory process of forming polar globules, 

 whereby the nucleolus, instead of becoming a homogeneous " Eikern," 

 forms at first a spindle-shaped " Eikern," and only indirectly the homo- 

 geneous nucleus. With the amphibians, finally, only a small portion 

 of the nuclear substance — perhaps a single nucleolus — furnishes the 

 diminutive nuclear structure. The last is a modification in the process 

 induced by the multi-miGleolav condition of the germinative vesicle. 



By studies on Ascaris nigrovenosa Brandt ('77) endeavors to refer 

 all the differences in the appearances presented by the germinative 

 vesicle, its supposed disappearance among others, to an amoeboid nature, 

 which induces constant change of form. This Brandt claims can be 

 directly observed. 



Much of the value which might otherwise attach to his observations is 

 lost from his not having supplemented his work with the proper use of 

 reagents, and from his ignoring the advantages of compression already 

 employed with such success by Auerbach. Brandt goes so far as to 

 express the opinion, that the substance of the germinative vesicle can 

 flow around and envelop the yolk, and that it can assume dendritic 

 forms, become diffuse, disappear, and again collect itself. 



With regard to the nuclei [pronuclei] discovered by Biitschli and 

 Auerbach, Brandt, although at first incredulous, satisfied himself of 

 their existence ; but instead of arising as minute spots or suddenly as 

 clear balls, they at first present, according to him, the appearance 

 of indistinct, diffuse spots of irregular shape, which, with constant 

 amoeboid change of form, at length become rounded, and then appear 

 most distinct. They are not, however, bodies sui generis, but rather 

 portions of the germinative vesicle that has become parted by amoeboid 

 motion, and is thus reconstructing itself. The mutual approach of 

 these pronuclei he explains as being brought about by a change in the 

 position of the pseudopodia ; still the yolk may concur in this move 



