198 Inheritance of Acquired Characters 
species can not only force this species to emigrate, or at 
least to widen its range of habitation, thus placing 
itself in contact with different telluric conditions and 
with different fauna and flora, but also it can itself 
induce directly very considerable modifications of the 
environment. 
Thus, to take an already famous example, it is pos- 
sible that the long neck and forelegs of the giraffe are 
to be ascribed to the overcrowding of the territory 
inhabited by its ancestors. For if we suppose that these 
ancestors at a definite time and in a definite region had 
become altogether too numerous in proportion to the 
trees present whose leaves served them for nourishment, 
then all the leaves up to a certain height would naturally 
have been eaten first, and there would finally remain only 
those leaves situated very high, so that in order to reach 
them the animal was forced to stretch out its neck with 
a greater effort than formerly and to stand upon its 
hind legs, falling later on the fore legs after plucking 
off the leaf. And these efforts so very different from the 
ordinary would have produced quite new morphological 
adaptations. But it is not at all necessary to suppose 
that all the individuals of this former species of giraffe 
were forced indiscriminately to this transformation. For 
many, perhaps becoming accustomed to another diet, could 
remain unaltered or undergo transformations of little 
importance. 
In other cases, on the contrary, that part of the 
species which was driven through overcrowding of the 
territory to change its diet would be compelled to undergo 
the most considerable transformations. This would be 
the case, for example, when the overcrowding of a given 
tract of meadow land by a species feeding exclusively 
