EEPTILES. 221 



they open into the mouth on each side near the lower jaw, and are 

 much distended during the croaking that is heard, especially in 

 spring and the beginning of summer, at pairing time 1 . In the 

 lizards the arytasno'id cartilages are usually present as distinct 

 pieces : in most serpents merely as processes at the posterior part 

 of the thyroid cartilage, and forming with it a whole. When the 

 larynx is more perfectly developed, the anterior apex of the 

 thyroid becomes free as an epiglottis. Most serpents and some 

 lizards have an epiglottis*. 



The kidneys in which, as in those of fishes, a cortical and a 

 medullary portion cannot be distinguished (p. 37), have in this class 

 a very various magnitude and form. They are much elongated 

 in the serpents, thick and oval in the tortoises, longitudinally oval 

 in lizards and batrachians. In the serpents the right kidney is 

 placed more forward than the left, in the others they lie more at the 

 same height, and often at the back part close together. In the 

 lizards they lie far backward, are attached to the sacrum, and 

 extend frequently under the tail. They are mostly incised at the 

 margin or divided into lobes by transverse grooves. In the 

 kidneys of serpents and tortoises these divisions on the surface 

 resemble the convolutions of the brain in mammals. The kidneys 

 are formed of tubules, which in some proceed immediately from the 

 ureters, and run transversely to the surface, where they terminate 

 blindly, whilst in others they leave the branches into which the 

 ureters divide for every lobe of the kidney. The ureters never pass 

 from a renal pelvis, but always arise from the successive union of 

 branches, or from the tubules of the renal substance itself. The 

 Malpighian bodies are present in reptiles as in the rest of the ver- 

 tebrate animals, and in the batrachians are sufficiently large to 

 be seen by the naked eye. In serpents the ureters are long, and 



1 P. CAMPER gave good figures of these parts, Verhandelingen van het Bataafsch 

 Genootsckap te Rotterdam, I. 1774, bl. 245 251, PI. X. These vesicles consist of two 

 membranes, the skin and a very thin production of the mucous membrane of the mouth. 

 The muscular coat of the skin compresses the internal membrane ; when the skin is 

 removed the vesicle can be much more largely distended by inflation than in the natural 

 state. 



2 HEXLE has given a general and comparative view of the larynx in this class, 

 illustrated throughout by the necessary figures, in his excellent VergleicTiend- 

 anatomische Beschreibung des Kehlkopfs. Leipzig, 1839, 4*- 



i 



