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 



