Recapitulation and Conclusion. 317 



is uo necessary or constant connection between the fer- 

 tilization of the ^gg and the sex of the embryo, and tlie 

 conchision which I have reached from the study of these 

 cases and of oar scanty information upon the subject 

 from otlier sources, is that sex is not determined by any 

 constant hxw; that in certain animals and j^lants the sex 

 of the embryo is determined by certain conditions, while 

 in other groups it is determined by quite different con- 

 ditions. 



However this may be, it is obvious that since perfect 

 males and perfect females may arise from eggs which 

 are fertilized, and also from eggs which are not fertil- 

 ized, the necessitv for fertilization does not come from 

 the necessity for transmitting to the offspring the or- 

 ganization of each parent. 



A review of the opinions and reasoning of various au- 

 thors shows that there is no good ground for believing 

 that the two reproductive elements play similar parts in 

 heredity and transmit every characteristic of each par- 

 ent. It is impossible to prove it by the phenomena of 

 crossing, since the only animals which can be made to 

 cross are essentially alike, and differ only in minor points. 

 The homolosrv between the ovum and the male cell is no 

 reason for supposing that their functions are similar. 

 There is no reason for assuming that each sex transmits 

 its entire organization to the offspring, since the latent 

 transmission of secondary sexual characters can be more 

 simply explained by assuming that each embryo inherits, 

 but does not necessarily develop, all the characteristics 

 of its species. 



Reversion and alternation of generations admit of 

 a similar explanation, and we may conclude that there 

 is and can be no proof that each sexual element transmits 

 all the characteristics of the ]3arent. There is therefore 



