v GENEEATIVE SYSTEM OF THE FEMALE 195 



the female proiiucleus, this also moves somewhat to meet it, until 

 the two come into contact dii the centre of the ovum and after 

 20 minutes form a new complete nucleus, which is immediately 

 surrounded by an aureola of homogeneous protoplasm from which 

 emanate the rays of a common star (Fig. 74). With the fusion of 

 the two pronuclei is fulfilled the great act of fertilisation, that is 

 the formation of the nucleus of segmentation, with which is 

 initiated the whole embryogenic process of a new being ; in other 

 words, the nucleus of segmentation represents the germ of the 

 individual to be born, because it contains all the determinants of 

 the characteristics, both somatic and psychic, which will go on 

 producing themselves and developing during ontogenetic evolution. 

 The glory of the discovery of these phenomena of the maturation 



Fio. 74. Fertilised ovum of echinoderm during the copula interna of the male pronucleus with 

 the female pronucleus. (According to O. Hertwig.) A, the head of the spermatozoon 

 having penetrated into the ovum is transformed into a spermatic nucleus (ns) or male pro- 

 nncku*, about which are formed protoplasmic rays ; the nucleus or female pronucleus (no) is 

 some distance from ns ; fi, no and ns approach, to fuse together in the complete nucleus of 

 wjinentation and are surrounded by star-like protoplasmic rays. 



and fertilisation of the ovum is divided amongst an elect band 

 of observers, of whom I will limit myself to indicating the most 

 meritorious : van Beneden (1883-87), Boveri (1887-90), 0. and 

 K. Hertwig (1875-90), Biitschli (1876-84), and Fol (1883-91). 

 Although these phenomena have been observed with greater 

 detail in the ova of the echinoderms and ascarides, there are not 

 wanting, however, observations on different classes of animals, in- 

 cluding the mammals, for example on the rabbit by van Beneden. 



There is no doubt then that they have a general value ; they 

 are confirmed, more or less modified in the more minute and 

 accessory particulars, throughout the animal kingdom. They 

 form the starting-point of many interesting considerations of a 

 philosophical character, to a few of which we shall with much 

 reserve make some reference. 



What are the differential characters of the two sexual 

 elements? What value or physiological significance must we 



