230 Evolution and Adaptation 
so, and have become fused, and can only be bent in and 
straightened out. The thighs, being bent out to clasp the 
larger branches, have caused the pelvis to widen, and, in con- 
sequence, the cotyloid cavities have become directed back- 
ward. Many of the bones of the skeleton have become 
fused, as a result of the immobility of the animal. 
Lamarck says, that “ Nature, in producing, successively, all 
the species of animals, beginning with the most imperfect, or 
the most simple, and terminating with the most perfect, has 
gradually complicated their organization. These animals 
becoming scattered throughout the habitable regions of the 
globe each species has received from the influences of its 
surroundings its present habits, and the modifications of the 
parts the use of which we recognize.”’ 
Such are Lamarck’s views and a fairly complete statement 
of the facts from which he draws his conclusions. His 
illustrations appear naive, and often not a little ludicrous, 
but it must be admitted that, despite their absurdities, his 
theory appears in some cases to account wonderfully well for 
the facts. The long legs of wading birds, the long neck and 
disproportionately long fore-legs of the giraffe, the structure 
of the sloth, and particularly the degeneration of the eyes of 
animals living in the dark, seem to find a simple explanation 
in the principle of the inheritance of acquired characters. 
But the crucial point of the entire theory is passed over in 
silence, or rather is taken for granted by Lamarck, namely, the 
inheritance in the offspring of the characters acquired through 
use or disuse in the parent. He-does not even discuss this 
topic, but in several places states unreservedly that the in- 
crease or decrease of a part reappears in the next generation. 
It is here that Lamarck’s theory has been attacked in more 
modern times, for as soon as experimental proof was de- 
manded to show that the results of use or of disuse of an 
organ is inherited, no such proof was forthcoming. Yet 
the theory is one that has the great merit of being capable of 
