466 GENERAL RESULTS. Chap. XII. 



place and followed the same habits of life. Nor can I 

 see reason to doubt that the widely different habits of 

 life of men and women in civilised nations, especially 

 amongst the upper classes, would tend to counter- 

 balance any evil from marriages between healthy and 

 somewhat closely related persons. 



Under a theoretical point of view it is some gain to 

 science to know that numberless structures in her- 

 maphrodite plants, and probably in hermaphrodite 

 animals, are special adaptations for securing an occa- 

 sional cross between two individuals; and that the 

 advantages from such a cross depend altogether on the 

 beings which are united, or their progenitors, having 

 had their sexual elements somewhat differentiated, so 

 that the embryo is benefited in the same manner as is 

 a mature plant or animal by a slight change in its 

 conditions of life, although in a much higher degree. 



Another and more important result may be deduced 

 from my observations. Eggs and seeds are highly 

 serviceable as a means of dissemination, but we now 

 know that fertile eggs can be produced without the 

 aid of the male. There are also many other methods 

 by which organisms can be propagated asexually. 

 Why then have the two sexes been developed, and 

 why do males exist which cannot themselves produce 

 offspring ? The answer lies, as I can hardly doubt, in 

 the great good which is derived from the fusion of two 

 somewhat differentiated individuals ; and with the 

 exception of the lowest organisms this is possible only 

 by means of the sexual elements, these consisting of 

 cells separated from the body, containing the germs of 

 every part, and capable of being fused completely 

 together. 



It has been shown in the present volume that the 



