ORGANIZATION OF REPTILES. 



1. Organs op Integumation. — ^We find in no other class of animals such a 

 variety of structure in the integuments, their characters differing in almost every 

 genus; horny in the Chelonia, scaly in the Serpents, smooth and soft in the Frogs, 

 vparty and tuberculous in the Toads. 



The cuticle exists in all. In the Tortoises it passes not only over the legs, but 

 over the shell; it covers the scales and plates of Lizards and Serpents; and in all, 

 is detached periodically. This character of shedding the cuticle is most observable 

 in the Serpents, where that structure is detached in the form of an entire covering; 

 in the Batrachia the cuticle is less distinct, resembling a mucous membrane, and 

 being shed in the water, it is frequently devoured by the animal itself This phe- 

 nomenon is not confined to the season of spring, as believed by Linnseus, but is 

 influenced by variations of temperature, the health of the animal, &c. I have 

 seen the Coluber guttatus change its skin four or five times during a confinement 

 of as many months. 



The rete mucosum is placed under the epidermis, and offers every variety of tint 

 and colour, as may be observed in different species of Reptiles; almost every 

 colour may be perceived in it — red, blue, green, yellow, varying in brightness, not 

 only in different individuals, but according to age, sex, &c. These shades are 

 always most remarkable when the skin has been newly cast. The tints in some 

 of the species, as in the Anolius and the Hylse, change according to the state 

 of excitement in the animal, or the activity of the circulation. 



