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 inthem. 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: 
“Tf we should consider as a result of degradation the 
loss of legs seen in the snakes, the Ophzdza 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 datrachians, which have them, offer a more 
