LAMARCK’S EXPLANATION 515 
early scientists, plants and animals are changed by their en- 
vironment, and these changes are then inherited by the offspring 
and retained as long as the environment remains constant. For 
example, according to this explanation, a plant, originally smooth 
but having been induced to become hairy through exposure to 
a drier climate, will impart the hairy feature to the offspring, 
which will maintain the modification until the environment so 
changes that hairiness is lost. In this way the origin of new char- 
acters and new species was explained. This assumes of course 
that a change in any part of the plant is recorded in the sperms 
and eggs of the plant and, therefore, transmitted to the progeny. 
Lamarck’s Explanation. — Lamarck, a noted French natur- 
alist whose views were published first in 1801 and in an en- 
larged form in 1809, offered the explanation which he called 
“ Appetency,”’ meaning desire. His explanation was based upon 
the observation that the organs of men and other animals are 
enlarged and strengthened by use and particularly by con- 
scious use. For example, it is common observation that one’s 
muscles enlarge and become stronger with proper use, while, 
on the other hand, with lack of use they decrease in size and 
strength. Long continued disuse may even result in the loss 
of an organ. 
There are three ideas involved in Lamarck’s explanation. 
First, his explanation assumes that the environment of animals 
and plants has been constantly changing, so that they have been 
constantly subjected to changes in temperature, moisture, light, 
nutrition, etc. Second, he believed that all living things have 
come from preéxisting forms as a result of changes which were 
responses to changes in the environment that made a new mode 
of life necessary. Thus the neck of the giraffe lengthened as 
a result of the animal’s effort to reach leaves on high branches. 
Also the form of the body of reptiles, such as snakes, which 
glide over the ground and conceal themselves in the Grass, is 
due to the mode of life which these animals have adopted. By 
repeated efforts of the animal to elongate in order to pass 
through small spaces, the body became extremely elongated and 
very narrow, and since long legs would raise the body too high 
from the ground and short legs would not move them rapidly 
enough, legs, vestiges of which are still in their plan of organiza- 
tion, were finally lost and another means of transportation was 
