5 i6 



MANUAL OF ZOOLOGY. 



for though they lose their branchiae when adult, they never- 

 theless retain the branchial apertures behind the head. 



Of the perennibranchiate Urodela, one of the best known 

 is the singular Proteus (Hypochthoii) anguinus (fig. 279), which 



is only found inhabiting pools 

 in certain caves in Illyria and 

 Dalmatia. It is of a pale flesh- 

 colour, or nearly white, with 

 three branchial tufts on each 

 side of the neck, while the 

 gill-slits are also persistent. 

 It attains a length of about a 

 foot, and has two pairs of weak 

 limbs, of which the anterior 

 have three toes, and the pos- 

 terior only two. From its hab- 

 itat, the power of vision must 

 be quite unnecessary, and, as 

 a matter of fact, the eyes are 

 altogether rudimentary, and 

 are covered by the skin. Sev- 

 eral varieties of Proteus are 

 known, and the one figured 

 above has been described as 

 a distinct species (P. xantho- 

 stictus). The blood-corpuscles 

 in Proteus are oval in shape, 

 and are larger than those of 

 any other vertebrate animal. 



Of the SirenidcB, the most 

 familiar are the Sirens and the 

 Axolotls. The Siren, or Mud- 

 eel (fig. 277, A), is found abun- 

 dantly in the rice-swamps of 

 South Carolina, and attains 

 a length of three feet. The 

 branchiae are persistent, and 

 the hinder pair of legs wholly 

 wanting. Two other species 

 are known, but they are like- 

 wise confined to North America. 



The Mexican Axolotl (Siredon pisdforme, fig. 280) is a 

 native of the Mexican lakes, and attains a length of about a 

 foot or fourteen inches. It possesses both pairs of limbs, the 

 anterior pair having four toes, and the hinder pair five toes. 



Fig. 280. The Axolotl (Siredon pisci- 

 forme) after Tegetmeier. The ordi- 

 nary form, with persistent branchiae. 



