VARIATION BY USE AND DISUSE. 261 
obstacles in our path in order to avoid them. If we 
could not do this we should run against objects, as 
we do in the dark. 
It is therefore clear that we need sight. This 
may have been developed by our surroundings them¬ 
selves. At first there may have come a little more 
Fig. 121.—An ostrich running. 
sensitiveness in one part of the body than in the 
others. This spot may have been put forward to feel 
the way, and thus grew more sensitive, until in time 
it changed its structure. These changes inherited and 
further intensified, finally resulted in a special organ, 
a primitive eye, which became ever more perfect, 
so that it recognized not only form in general but 
color, detecting the slightest differences in lights and 
shadows, until we have the artist’s eye. 
In like manner, hearing, smell, and taste were de¬ 
veloped, according to the theory of Lamarck. 
Our environment includes all things that influence 
18 
