II 



EXTERNAL FEATURES AND VARIETIES 



EXTERNAL FEATURES 



The external form of the Salamander is one of the simplest which it 

 is possible for a terrestrial, tetrapodous vertebrate to have. The 

 head is broad and flattened like that of the Frog, but the snout is 

 rather more rounded. The eyes stand up prominently from the sur- 

 face of the head, while the small external nares may be seen in front 

 of them on either side of the snout. The naso-lacrymal duct opens to 

 the exterior at the anterior corner of the eye by means of a fine pore 

 which is visible only by the aid of a lens. The apparent gape (see also 

 p. 2 62) extends to a little behind the posterior corner of the eye, and the 

 upper jaw slightly overhangs the lower. On the dorsal surface of the 

 head, just behind the eyes, is a pair of large reniform protuberances, 

 the paratoid glands (see also p. 292). They are very characteristic 

 of the animal. There is no true neck but there is a slight narrowing of 

 the contour behind the head, due largely to these paratoid glands, 

 while ventrally there is a distinct fold in the skin marking off the 

 head from the pectoral region. This is th^gularfold^ and represents the 

 line of fusion between the larval gill cover, or operculum, and the skin. 



The trunk is roughly cylindrical, while the sides of the body pre- 

 sent a wrinkled appearance due to the fact that the skin is closely 

 adherent to the myosepta but free in between. 



The tail tapers, at first rapidly, and then more gradually, and 

 finally terminates in a blunt point. It is very slightly flattened laterally. 



Extending from behind the head to the tip of the tail, in the mid- 

 dorsal line, is a double row of cutaneous poison glands of a similar 

 nature to those forming the paratoids. These series of venom- 

 secreting glands are dealt with in more detail on p. 292. 



The limbs are relatively small, particularly the fore-limbs. Thus 

 mechanically, as well as in many other ways, the Salamander is truly 

 intermediate between the piscine structure, where practically the 

 whole of the animal — apart from the skeleton — is composed of 

 segmental body muscles and viscera, and that of the typical land 

 vertebrate, in which the muscles associated with the limbs tend to 

 predominate over those of the trunk and tail. 



The total body length of adult specimens, including the tail, 



