v GENEEATIVE SYSTEM OF THE FEMALE 197 



These assertions contradict the hypothesis of hermaphroditism 

 of the nuclei maintained by Minot (1882) and specially by van 

 Beneden (1884). This hypothesis is founded on the phenomena of 

 maturation of the ovum, by which the polar bodies separate, and 

 the equivalent phenomena of the detachment of the spermatozoa 

 from the spermatoblasts. The nuclei of the ova and of the 

 spermatozoa before their maturation would be hermaphrodite ; 

 the former do not acquire their female sexual characters until 

 after they have rid themselves of the male parts of their herma- 

 phrodite nuclear apparatus by the elimination of the polar bodies ; 

 the latter do not acquire their male character until they have 

 abandoned in the spermatoblast the female part of their herma- 

 phrodite nucleus. After maturation, the pronucleus of the ovum, 

 and the pronucleus of the spermatozoa acquire opposite sexual 

 characters, and fecundation consists in the substitution of the 

 male elements expelled from the ovum by those conveyed to the 

 ovum by the spermatozoon. This ingenious theory of the herma- 

 phroditism of the immature sexual elements, and the substitution 

 of the male sexual part of the ovum by that of the spermatozoon 

 in the act of fecundation, does not bear critical examination along- 

 side better ascertained facts relative to the process of reproduc- 

 tion in the whole world of living beings, which demonstrate 

 original asexuality, that is the equivalence of the male and 

 female pronuclei, from the fusion of which results the germ of the 

 new being. According to this view, the maturation of the ovum, 

 meaning thereby the expulsion of the polar bodies, does not 

 signify the transformation of a hermaphrodite element into a 

 female element, but simply the diminution by half of the nuclear 

 substance, the chromatin of the ovum, so as to render possible 

 the substitution of another equivalent substance, different only 

 in proceeding from another individual sexually differentiated. 

 Without going through the vast field of the comparative physio- 

 logy of fecundation, we will limit ourselves to summing up in a 

 few general propositions the results of numerous observations, 

 confining ourselves specially to the studies of 0. Hertwig. 



(a) In order that fertilisation may occur, it is necessary that 

 the sexual elements be fertile, that is, possess certain definite 

 tendencies, and be sexually akin, in other words, reciprocally 

 adapted one to the other and with a tendency to unite. We are 

 as yet ignorant of the real nature of fertility and sexual affinity. 



(6) Fertility presents itself periodically in the life of the cell ; 

 it is of short duration ; it depends to a certain extent on external 

 influences, and in many cases may be abolished and transformed 

 into parthenogenesis, i.e. virgin generation, or into apogamia, i.e. 

 alternation of generation. 



(c) Sexual affinity is expressed by the reciprocal action which 

 the fertile elements exercise at a certain distance, so that they 



