4 
INTRODUCTION. 
generations, some bird had given birth to a woodpecker, 
and some plant to the missletoe, and that these had 
been produced perfect as we now see them; but this 
assumption seems to me to be no explanation, for it 
leaves the case of the coadaptations of organic beings to 
each other and to their physical conditions of life, un¬ 
touched and unexplained. 
It is, therefore, of the highest importance to gain a 
clear insight into the means of modification and co¬ 
adaptation. At the commencement of my observations 
it seemed to me probable that a careful study of domes¬ 
ticated animals and of cultivated plants would offer the 
best chance of making out this obscure problem. Nor 
have I been disappointed; in this and in all other 
perplexing cases I have invariably found that our 
knowledge, imperfect though it be, of variation under 
domestication, afforded the best and safest clue. I may 
venture to express my conviction of the high value of 
such studies, although they have been very commonly 
neglected by naturalists. 
From these considerations, I shall devote the first 
chapter of this Abstract to Variation under Domestication. 
We shall thus see that a large amount of hereditary 
modification is at least possible ; and, what is equally or 
more important, we shall see how gTeat is the power of 
man in accumulating by his Selection successive slight 
variations. I will then pass on to the variability of 
species in a state of nature; but I shall, unfortunately, 
be'compelled to treat this subject far too briefly, as it 
can be treated properly only by giving long catalogues 
of facts. We shall, however, be enabled to discuss 
what circumstances are most favourable to variation. 
In the next chapter the Struggle for Existence amongst 
all organic beings throughout the world, which inevi¬ 
tably follows from the high geometrical ratio of their 
