OF MICE 0- OR GANISMS. 1 03 



phenomena relative to fecundation. Fecundation con- 

 sists in the fusion of two nuclei, of which one proceeds 

 from the male, and one from the female. Thus, it is 

 through the intermediary office of the nucleus that all 

 the faculties, all the properties possessed by the par- 

 ents, — the form of their bodies as well as their psychi- 

 cal faculties, — are transmitted to the embryo; as we 

 have just remarked, therefore, all these properties 

 must be comprehended in the nucleus, in order to pass 

 into the embryo. 



We must note further, that the embryo takes from 

 the mother something besides the nucleus. While it is 

 connected with the father through the head of the 

 spermatozoid, which has the morphological value of a 

 nucleus, it receives from the mother not only the fe- 

 male nucleus but also the vitelline plasma of the 

 ovule; now, as the embryo does not exhibit a greater 

 morphological likeness to the mother than to the fa- 

 ther, we may thence infer that the vitelline protoplasm 

 inherited from the mother exerts no formative influ- 

 ence upon the development of its body. 



These are not the only facts the connection of 

 which we desire to show with the results of experi- 

 ments upon the function of the nucleus. It will be well 

 to point out here, how reproduction is effected among 

 organisms which, besides their nucleus, possess other 

 differentiated organs. The best known and perhaps 

 the most general mode of reproduction is fissiparity, 

 which consists in a division of the entire body into two 

 equal parts. If we closely follow the course of this 

 phenomenon in any organism whatever, we shall find 

 that the division begins by a multiplication of the 

 principal organs of the body. The nucleus begins by 

 lengthening out and assuming a position perpendicu- 



