The Theory of Natural Selection. 255 
adapted to browsing on high foliage. And so in the 
cases of other animals, Lamarck believed that the 
adaptation of their forms to their habits could be ex- 
plained by this simple hypothesis that the habits 
created the forms, through the effects of use and dis- 
use, coupled with heredity. 
Such is what is ordinarily known as Lamarck's 
theory of evolution. We may as well remember, 
however, that it really constitutes only one part of his 
theory ; for besides this hypothesis of the cumulative 
inheritance of functionally-produced modifications—to 
which we may add the inherited effects of any direct 
action exercised by surrounding conditions of life,— 
Lamarck believed in some transcendental principle 
tending to produce gradual improvement in pre-de- 
termined lines of advance. Therefore it would really 
be more correct to designate the former hypothesis by 
the name either of Erasmus Darwin, or, still better, of 
Herbert Spencer. Nevertheless, in order to avoid con- 
fusion, I will follow established custom, and subse- 
quently speak of this hypothesis as the Lamarckian 
hypothesis—understanding, however, that in employ- 
ing this designation I am not referring to any part 
or factor of Lamarck’s general theory of evolution 
other than the one which has just been described— 
namely, the hypothesis of the cumulative transmission 
of functionally-produced, or otherwise “acquired,” 
modifications. 
This, then, was the earliest hypothesis touching the 
causes of organic evolution. But we may at once 
perceive that it is insufficient to explain all that stands 
to be explained. In the first place, it refers in chief 
part only to the higher animals, which are actuated to 
