Inheritance of Acquired Characters 249 
higher branches could not be the cause of the lengthening of 
the legs. But “the coadaptation of the parts, required to make 
the giraffe’s structure useful, is much greater than at first 
appears.” For example, the bones and the muscles of the 
hind-legs have been also altered, and Spencer argues that it 
is “impossible to believe’’ that all parts of the hind-quarters 
could have been coadapted to one another, and to all parts 
of the fore-quarters. A lack of coadaptation of a single muscle 
“would cause fatal results when high speed had to be main- 
tained while escaping from an enemy.” 
Spencer claims that, since 1886, when he first published 
this argument, nothing like an adequate response has been 
made; and I think he might have added that an adequate 
answer is not likely to be forthcoming, since nothing short 
of a demonstration of how the giraffe really evolved is 
likely to be considered as sufficient. Wallace’s reply, that 
the changes in question could have been brought about 
by natural selection, since similar changes have been brought 
about by artificial selection, is regarded as inadequate by 
Spencer, since it assumes a parallel which does not exist. 
Nevertheless, Wallace’s reply contains, in my opinion, the 
kernel of the explanation, in so far as it assumes that con- 
genital variation! may suffice to account for the origin of 
a form even as bizarre as that of the giraffe. The ancon 
ram and the turnspit dog were marked departures from the 
normal types, and yet their parts were sufficiently codrdi- 
nated for them to carry out the usual modes of progression. 
It would not have been difficult, if we adopted Spencer’s 
mode of arguing, to show that these new forms could not 
possibly have arisen as the result of congenital variations. 
Again, it might be argued that the large, powerful dray- 
horse could not have arisen through a series of variations 
from the ordinary horse, because, even if variations in the 
1 Wallace assumes fluctuating variation to suffice, but in this I cannot agree 
with him. 
