234 Evolution and Adaptation 



alike in -every detail of structure. I am aware that my view 

 is merely a provisional hypothesis or speculation ; but, until 

 a better one be advanced, it will serve to bring together a 

 multitude of facts which are at present left disconnected by 

 any efficient cause." 



In presenting the hypothesis of pangenesis Darwin begins 

 by enumerating the different kinds of sexual and asexual 

 processes of reproduction, for which he hopes to offer a 

 provisional explanation. Here we find mentioned various 

 methods of budding and self-division, regeneration, partheno- 

 genesis, sexual reproduction, and the inheritance of acquired 

 characters. It is with the last only that we are here chiefly 

 concerned ; in fact, the need of an hypothesis of this sort to 

 explain the other kinds of inheritance is by no means evident. 

 There are, however, two other phenomena, besides that of the 

 supposed inheritance of acquired characters, to which the 

 hypothesis of pangenesis might appear to apply specially, 

 namely, the effect of foreign pollen on the tissues of the 

 mother plant, and the supposed influence of the union with 

 the first male on the subsequent young (telegony). It is, 

 however, far from being shown that any influence of this 

 latter kind really occurs, despite the fact that it is generally 

 believed in by breeders. 



It is important to observe that Darwin proposes to explain 

 on the hypothesis of pangenesis, not only the inheritance of 

 characters acquired through use, but also the decrease of 

 structures through disuse ; and this applies, not only to the 

 structure, but to function as well, as when the intelligence of 

 the dog is explained through his association with man, and 

 the tameness of the domestic rabbits through their long con- 

 finement. In the following quotation these points are referred 

 to : " How can the use or disuse of a particular limb or of the 

 brain affect a small aggregate of reproductive cells, seated in 

 a distant part of the body, in such a manner that the being 

 developed from these cells inherits the characters of either 



