uggests the belief that the entailed modifications are much more
numerous and remote than at first appears; and that the greater part of
these are such as cannot be ascribed in any degree to the selection of
favourable variations, but must be ascribed exclusively to the inherited
effects of changed functions. Whoever has seen a giraffe gallop will
long remember the sight as a ludicrous one. The reason for the
strangeness of the motions is obvious. Though the fore limbs and the
hind limbs differ so much in length, yet in galloping they have to keep
pace--must take equal strides. The result is that at each stride, the
angle which the hind limbs describe round their centre of motion is much
larger than the angle described by the fore limbs. And beyond this, as
an aid in equalizing the strides, the hind part of the back is at each
stride bent very much downwards and forwards. Hence the hind-quarters
appear to be doing nearly all the work. Now a moment's observation shows
that the bones and muscles composing the hind-quarters of the giraffe,
perform actions differing in one or other way and degree, from the
actions performed by the homologous bones and muscles in a mammal of
ordinary proportions, and from those in the ancestral mammal which gave
origin to the giraffe. Each further stage of that growth which produced
the large fore-quarters and neck, entailed some adapted change in sundry
of the numerous parts composing the hind-quarters; since any failure in
the adjustment of their respective strengths would entail some defect in
speed and consequent loss of life when chased. It needs but to remember
how, when continuing to walk with a blistered foot, the taking of steps
in such a modified way as to diminish pressure on the sore point, soon
produces aching of muscles which are called into unusual action, to see
that over-straining of any one of the muscles of the giraffe's
hind-quarters might quickly incapacitate the animal when putting out all
its powers to escape; and to be a few yards behind others would cause
death. Hence if we are debarred from assuming that co-operative parts
vary together even when adjacent and closely united--if we are still
more debarred from assuming that with increased length of fore-legs or
of neck, there will go an appropriate change in any one muscle or bone
in the hind-quarters; how entirely out of the question it is to assume
that there will simultaneously take place the appropriate changes in