298 Darwin and Pangenesis. [ July, 
nature; and although such a view may be seized upon by the 
opponents of the theory as an admission that there zs a limit to 
variation, and that therefore no new species can thus have been 
brought into existence (a corollary which by no means results from 
our proposition), yet we find that in the work before us the author 
quite concurs with our views, excepting that he seeks to explain 
how hybridism is affected by nature, whilst we contented our- 
selves with suggesting that Providence does bring about such 
results, without as yet seeing clearly by what means they are 
effected. He first compares the phenomena relating to this subject 
in domesticated animals with those in a state of nature :—“ On the 
principle which makes it necessary for man, whilst he is selecting 
and improving his domestic varieties, to keep them separate, it 
would clearly be advantageous to varieties in a state of nature, that 
is, to incipient species, if they could be kept from blending, either 
through sexual aversion or by becoming mutually sterile. Hence 
it at one time appeared to me probable, as it has to others, that 
this sterility might have been acquired through natural selection. 
On this pomt we must suppose that a shade of lessened fertility 
first spontaneously appeared, like any other modification, in certain 
individuals of a species when crossed with other individuals of the 
same species, and that successive degrees of infertility, from being 
advantageous, were slowly accumuiated.” * 
The words italicized by us show that the author had thus only 
removed the difficulty a little farther from view than before, but 
he has now come to the conclusion that “species have not been 
rendered mutually infertile through the accumulative action of 
natural selection ;” .. . “ that they have not been endowed through 
an act of creation with this quality ;” but that “it has arisen inci- 
dentally during their slow formation in connection with other and 
unknown changes in their organization.” | The word (again under- 
lined by us) would lead one to think that the difficulty remains to 
the author pretty much where it was; but the context shows that 
he attributes the changes in the reproductive system leading to 
hybridism to a correlative variation in the whole living form, that 
is, that when the whole fabric changes, that portion of it which 
perpetuates the animal changes also, and the ultimate agency is 
again “pangenesis ;” but then again he says, “ Pangenesis does not 
throw much light on hybridism.” t 
There is another view taken by the author, of the occurrence 
and effect of hybridism in nature, which deserves mention. He 
finds that when wild animals are at first domesticated, the sudden 
change in the surrounding conditions of their life renders them for 
a time infertile: “numerous facts,” he says, “have been given, 
* « Animals and Plants under Domestication,’ vol. ii., p. 185. 
+ Ibid., p. 188. t Ibid., p. 385. 
