LIZARDS. 129 



ent on a peculiarity of structure no less singular, 

 first noticed by Cuvier. That illustrious physio- 

 logist considers it a very interesting fact that a 

 great number of the vertebras of the tail in the 

 common Lizards are divided in the middle in a 

 vertical plane into two portions ; and that these 

 portions are separated with even more facility 

 than two contiguous vertebrae at the point of ar- 

 ticulation ; and this for the simple reason that the 

 articulation is compHcated, formed of many irre- 

 gularities of surface {apophyses), and strengthened 

 by ligaments, while the adhesion of the two parts 

 of each vertebra is retained only by the continuous 

 periosteum (or membrane that invests the bone), 

 and by the surrounding tendons. This structure 

 he had observed besides in the Iguance and the 

 Anoles, and is of opinion that it would be found 

 in all the genera which, like those mentioned, are 

 subject to the rupture of the tail. " Every one 

 knows," adds this anatomist, " that the tail shoots 

 out again after having been broken, but neither 

 the skeleton nor its integuments are, in that case, 

 the same as before the rupture. The scales of 

 the skin are generally small, without ridges and 

 without spines, though they may have had the 

 contrary qualities in the original tail ; and inter- 

 nally, instead of the numerous vertebrae, with all 

 their apparatus of apophyses and ligaments, there 

 is nothing but a long cartilaginous cone of one 

 piece, which only presents annular wrinkles, nu- 

 merous indeed, but scarcely at all elevated." We 

 have some reasons for thinking, however, that in 

 time the reproduced tail would assume at least the 

 exterior appearance, if not the interior structure 

 of the original member. 



K 



