1 6 BIOLOGICAL LECTURES. 



tion, concludes with these words :^ "Their union [that of the 

 Q%% and sperm nucleus] is not the condition but the goal of 

 fertilization, and in this sense the statement is true to-day in 

 which O. Hertwig summed up the results of his first funda- 

 mental investigations, that ' the essential thing iji fertilization is 

 the union of egg and spcnii nucleus' " 



It is only within the most recent times that a different view 

 has arisen, and for the sake of clearness I will sketch briefly 

 the rise of the idea that fertilization is not a purely nuclear 

 phenomenon, that it does not consist simply in a union of 

 nuclei coming from different individuals, but rather, as it seems 

 to me, in a union of all the essential parts of the reproductive 

 cells, cytoplasm as well as nuclei. 



In 1873 Hermann FoP described in the eggs of a jelly-fish 

 two star-shaped figures or asters at the two poles of the 

 nucleus, and one year later E. Van Beneden ^ described a 

 polar corpjtscle as present in the cytoplasm during the karyoki- 

 netic division of the nucleus in some small parasitic organisms, 

 the Dicyemidae ; but it was certainly not until a much later 

 date that anything satisfactory was known of these bodies. 



In 1887, only six years ago. Van Beneden'* in his work on 

 the fertilization of the ^^g of Ascaris, a thread-worm inhabit- 

 ing the intestine of the horse, gave a very minute account 

 of two granular bodies, the sphtres attractives which he 

 believed to be present at all times in the cytoplasm of the cell. 

 He described each sphere as consisting of a central refractive 

 body, the cejitral corpuscle, around which was a clear space, the 

 tnedullary zone, which in turn was surrounded by a deeply 

 staining granular area, the cortical zone, Fig. i, A and C. 

 Although he regarded these spheres as permanent organs of 

 the cell, he did not know how they originated in the Q.%g under- 

 going fertilization, but he thought that tlie two spheres appeared 

 simultaneously in the egg as newly formed structures, and he 



1 Loc. cit., p. 433. 



2 Hermann Fol, Die erste Ijitwicklung ties (leryonideneies. Jenaische Ziit- 

 schrift, 1873. 



3 E. Van lieneden, Recherches sur les Dicyemides. Ihill. Acad. roy. Bcti^., 1S74. 

 * Van licneden et Xeyt, Nouvelles Recherches sur la Fecondation et la Division 



mitosique chez I'Ascaride megalocephale. 



