56i 
they are mere individual variations which are perfectly 
consistent with fixity of species. 
In order to prove that Natural Selection was the only 
key to solve this problem, it would be necessary to show 
that an existing generation of a species had the tendons 
attached to the bones in a different way to that in which 
they had been attached some generations previously. It 
would be necessary to show that the present attachment 
had prevailed over the previous one by the survival of 
the one set of variants and the destruction of the other. 
It is impossible to prove this, unless we dissected all the 
individuals of each generation of a group of animals. 
“ The relations of bones to tendons is not always the 
same.” That must mean that in each generation indi 
viduals are differently constituted. Does this difference 
make any difference to the animals ? In order to prove 
this you would have to establish a correlation between 
the most active or the most powerful limbs and one or 
other of their different modes of attachment. You must 
compare their several degrees of capability and strength ; 
and then by dissection ascertain whether difference in the 
attachment of tendons to bones is the cause. 
Again, it may be safely assumed that the mode of 
attachment normal to a species would be best adapted to 
the wants of its individuals. Any deviations which were 
very slight could not be of any advantage or disadvantage; 
if they were considerable, they might not be advantageous, 
and could not be preserved by the means of Natural 
Selection. If a slight modification in the attachment of 
the tendon were accompanied by a slight modification of 
the contour of the bone, the phenomenon would be ex 
plained by the correlation of growth which changes one 
co-ordinated structure into another ; but in order that the 
new modification should be preserved by Natural Selection, 
JJ