i877-j 
Evolution by Expansion. 
37 
yet distinctly different in continents or traCts separated by 
natural barriers, would indicate not so much relationship as 
expansion from a similar source by the same laws, the slight 
divergence of character being due to a difference in the con- 
ditions of existence. 
I have not yet touched on the subjects of instinCt, organs 
of high perfect ion, and the evidences of design : they do not 
appear to me to admit of the exaCt reasoning applicable to, 
and the strictly logical conclusions deducible from, the 
leading faCts — the grand truths of natural history on which 
I have in this paper based my arguments in support of the 
theory of evolution by expansion. 
Darwin is well aware of the difficulties they present 
to the theory of natural selection, and he has met these 
difficulties by arguments more admirable for their ingenuity 
than for their conclusiveness. Thus, he says of instinCt, — 
“ Many instinCts are so wonderful that their development 
will probably appear to the reader a difficulty sufficient to 
overthrow my whole theory. I may here premise that I 
have nothing to do with the origin of the mental powers, any 
more than I have with that of life itself. We are concerned 
only with the diversities of instinCt and of the other mental 
faculties in animals of the same class.” 
He here avoids raising a query that can, it seems to me, 
admit of only one answer. 
The same difficulty occurs to him in connection with 
organs of extreme perfection, and is disposed of in the 
same way. Thus he says — “ To suppose that the eye, with 
all its admirable contrivances for adjusting the focus to dif- 
ferent distances, for admitting different amounts of light, 
and for the correction of spherical and chromatic aberration, 
could have been formed by natural selection, seems, I freely 
confess, absurd in the highest degree. When it was first 
said that the sun stood still and the world turned round, the 
common sense of mankind declared the doCtrine false, but 
the old saying of Vox populi vox Dei, as every philosopher 
knows, cannot be trusted in Science. Reason tells me that 
if numerous gradations from a simple and imperfeCt eye to 
one complex and perfect can be shown to exist, each grade 
being useful to its possessor, as is certainly the case ; if, 
further, the eye ever varies and the variations are inherited, 
as is certainly likewise the case ; and if such variations 
should be useful, under changing conditions of life, then the 
difficulty of believing that a perfect and complex eye could 
be formed by natural selection, though insuperable by our 
imagination, should not be considered subversive of the 
