290 LAMARCK, HIS LIFE AND WORK 



to bring out clearly the successive steps in inferiority 

 or degradation presented in descending the animal scale. 

 ' We will glean some passages of this chapter which 

 bear on his theory of descent. Speaking of the 

 different kinds of aquatic surroundings he remarks : 



" In the first place it should be observed that in 

 the waters themselves she [Nature] presents consider- 

 ably diversified circumstances; the fresh waters, marine 

 waters, calm or stagnant waters, running waters or 

 streams, the waters of warm climates, those of cold 

 regions, finally those which are shallow and those 

 which are very deep, offer many special circum- 

 stances, each of which acts differently on the animals 

 living in them. Now, in a degree equal to the make- 

 up of the organization, the races of animals which are 

 exposed to either of these circumstances have been 

 submitted to special influences and have been diver- 

 sified by them." 



He then, after referring to the general degradation 

 of the Batrachians, touches upon the atrophy of legs 

 which has taken place in the snakes : 



" If we should consider as a result of degradation the 

 loss of legs seen in the snakes, the Ophidia should be 

 regarded as constituting the lowest order of reptiles ; 

 but it would be an error to admit this consideration. 

 Indeed, the serpents being animals which, in order to 

 hide themselves, have adopted the habit of gliding 

 directly along the ground, their body has lengthened 

 very considerably and disproportionately to its thick- 

 ness. Now, elongated legs proving disadvantageous 

 to their necessity of gliding and hiding, very short 

 legs, being only four in number, since they are verte- 

 brate animals, would be incapable of moving their 

 bodies. Thus the habits of these animals have been 

 the cause of the disappearance of their legs, and yet 

 the batrachians, which have them, offer a more 



