82 THE PSYCHIC LIFE 



just as among all animals; it is the most agile and 

 the stoutest spermatozoid that first penetrates the ovule 

 and effects fecundation. The laws of selection, thor- 

 oughly developed by Darwin, do not only apply to in- 

 dividuals; they apply also to sexual elements. 



We are unable to follow the successive modifica- 

 tions suffered by the head of the spermatozoid after 

 its entrance into the ovule; we may state simply, that 

 the head presents the appearance of a radiate figure, 

 of a diminutive sun advancing towards the female nu- 

 cleus. At the same moment, the female nucleus ap- 

 pears affected and puts itself in motion towards the 

 spermatic nucleus. The two nuclei soon come almost 

 within contact, and it is in particular the female nu- 

 cleus that then plays the active part. It is disturbed 

 by incessant movements and every moment changes 

 its form; it thrusts out prolongations towards the male 

 nucleus, and one of these prolongations fastens itself 

 upon the latter, presenting at the end a minute de- 

 pression in the shape of a cup, which receives the male 

 nucleus; and the two nuclei, while executing active 

 movements, fuse into one another. In this manner 

 the first nucleus of segmentation is created. 



Selenka has furnished interesting chronological 

 data as to the time of appearance of the different phe- 

 nomena. The time is in each case taken from the mo- 

 ment of artificial fecundation. After a lapse of five 

 minutes, the spermatozoid has forced an entrance into 

 the ovule.* At the expiration of ten minutes (that is, 

 five minutes after entrance), it has reached the centre 

 of the ovule. At twelve minutes, the female nucleus 

 has put itself in motion to meet the spermatic nucle- 



* M. Balbiani, Cours sur lafecondation, passim. Journal de Rficrographze 

 Vol. III. 1879. 



