ORDER OPHIDIA. 287 



malia, and walking birds — swimming birds, and flying fishes, 

 — ^in short, some out of each borrow the characters of others, 

 and lose some of those peculiar to their own division. 



In consequence of such affinities, which are for the most 

 part but external, it is incumbent on every person, who is 

 desirous of fathoming the history of the animals on which we 

 are now writing, to study attentively their internal organiza- 

 tion, and by means of it, to establish the points of compari- 

 son which throw light on the theory of their classification. 

 We shall therefore now briefly touch upon their different 

 organs, beginning with those of locomotion. 



Progression takes place in these animals by means of sinu- 

 osities and springs executed in the water, or on the ground, 

 by a true reptation, as well as by the faculty which many of 

 them possess of contorting themselves, and consequently 

 climbing around the branches of trees. 



The ophidians, then, are eminently reptiles, and their rep- 

 tation consists in an impulse of the body forwards or back- 

 wards by an alternate movement of one or several of its un- 

 der parts against the ground. This movement takes place 

 in various ways ; sometimes by vertical waves or swellings, 

 as in the adder of Esculapius. Sometimes these windings 

 are horizontal, an example of which is the collared adder. 

 Sometimes the posterior region of the body alone contributes 

 to the motion, while its anterior part is raised vertically. 

 Sometimes it is performed by a series of gentle undulations, 

 owing to the alternate approximation and separation of the 

 transverse plates of the abdomen and the tail, or by an ana- 

 logous action of the rings of the body, as in the amphis- 

 bcenae. 



When they repose on the earth, they form with their body 

 several circles placed one above the other, or around the 

 others, and surmounted by the head. It is by the sud- 

 den deploying of all these circles, or a part of them only, 



