556 BIOLOGY. 



naked ; in others Mussel-shells originate, as in the 

 carapace of the Tortoises ; the scales, scutes, and claws 

 of Serpents and Lizards repeat the rings and scutes of 

 Crabs. 



3378. The head has separated itself more from the 

 thorax, the eyes and ears being much more perfect ; as 

 regards the latter organs the cranium is always perfo- 

 rated, in the former there are eyelids. 



3379. The eyes have still no power of free motion, and 

 the eyelids are as yet very imperfect. It is principally 

 the lower eyelid which closes, while in Mammalia the 

 upper one is the most developed. 



3380. The external auditory meatus is notwithstand- 

 ing usually covered by integument, the auditory ossicles 

 are mostly blended into one, which projects above the 

 skull ; the cochlea is wanting. 



3381. Reptiles produce sounds for the first time 

 through the lungs ; they have voice, but as yet no song. 



3382. The nose, however, gives the finishing touch to 

 the head. It has not only opened as a vertebral canal 

 in front, but also as a thoracic cavity posteriorly into the 

 mouth, which was not the case in Fishes. The open 

 nose is the aesthetic character of Reptiles, just as the 

 red muscles are the characteristics of the anatomical 

 systems. The Reptiles are Rhwozoa. 



3383. The tongue takes a higher rank than in Fishes. 

 It is throughout soft, fleshy, and smooth ; but in most 

 species is still slit into two, which reminds us of a similar 

 condition of the penis. 



3384. The teeth are in these animals more like digits 

 than in Fishes. While here they consist for the greatest 

 part of front teeth, and are therefore associated with the 

 intestine, in Reptiles they are mostly lateral, and thus 

 true maxillary teeth, which are annexed to the salivary 

 system. With this special dental formation the saliva is 

 also more active ; it is a rapidly fatal poison. 



3385. The poison-teeth or fangs have likewise a groove, 

 which can be regarded as the continuation of the salivary 

 duct. 



