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 ¢hzs 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 
