Recapitulation and Conclusion. 317 



is 110 necessary or constant connection between the fer- 

 tilization of the egg and the sex of the embryo, and the 

 conclusion which I have reached from the study of these 



cases and of our scanty information upon the subject 



from other sources, is that sex is not determined by any / 

 constant law; that in certain animals and plants the sex / 

 of the embryo is determined by certain conditions, while / 

 in other groups it is determined by quite different cos J 

 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 necessity 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 homology 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 parent. There is therefore 



