LAMARCK ON ADAPTATION. II5 
have arisen from the habit of fetching their food out of 
narrow, small, and deep crevices or channels. The webs 
between the toes of the webbed feet in frogs and other 
aquatic animals have arisen solely from the constant endea- 
your to swim, from striking their feet against the water, 
and from the very movements of swimming. Inheritance 
fixed these habits on the descendants, and finally, by further 
elaboration, the organs were entirely transformed. However 
correct, as a whole, this fundamental thought may be, yet 
Lamarck lays the stress too exclusively on habit (use and 
non-use of organs), certainly one of the most important, but 
not the only cause of the change of forms. Still this cannot 
prevent our acknowledging that Lamarck quite correctly 
appreciated the mutual co-operation of the two organic 
formative tendencies of Adaptation and Inheritance. What 
he failed to grasp is the exceedingly important principle of 
“Natural Selection in the Struggle for Existence,” with 
which Darwin, fifty years later, made us acquainted. 
It still remains to be mentioned as a special merit of 
Lamarck, that he endeavoured to prove the development of 
the human race from other primitive, ape-like mammals. 
Here again it was, above all, to habit that he ascribed the 
transforming, the ennobling influence. He assumed that the 
lowest, original men had originated out of men-like apes, by 
the latter accustoming themselves to walk upright. The 
raising of the body, the constant effort to keep upright, in 
the first place led to a transformation of the limbs, to a 
stronger differentiation or separation of the fore and hinder 
extremities, which is justly considered one of the most 
essential distinctions between man and the ape. Behind, 
the calf of the leg and the flat soles of the feet were 
