CLASS AMPHIBIA 



373 



They have a harsh, warty skin, ridges on the head, and a kidney-shaped 

 raised area behind the head on each side known as the parotoid gland (Fig. 

 264). When disturbed, toads frequently pass water from the bladder, 

 and the superstition is widely spread to the effect that the handling of 

 a toad will cause warts. They are nocturnal in habits, feeding upon 

 insects, worms, and snails. Their skins contain glands which produce 

 noxious secretions and they are therefore rarely eaten by other animals. 

 The frogs have a body which is somewhat spindle-shaped, pointed 

 anteriorly, and rounded posteriorly. The forelegs are weak and the 

 toes only slightly webbed; but the hind ones are long and strongly 

 muscled, \\dth long, fully webbed toes, fitting them for leaping and 

 swimming. On superficial examination the male of common frogs 

 may be distinguished from the female by the greater thickness of the 



Fig. 262. — Common eastern tree 

 toad, Hyla versicolor heConte. Male, 

 from Staten Island, New York, 

 X %. (Redrawn from Dicker son. 

 "Frog Book:') 



Fig. 263. — .\siatic cecilian, Ich- 

 thyophis sp., with eggs. (Modified 

 from Thomson, " OutliTies of Zoology," 

 after P. and F. Sarasin.) 



inmost digit of the forefoot. The metamerism of the body wall is 

 greatly obscured, this being due in part to the shortness and compactness 

 of the body and in part to the development of muscles connecting the 

 limbs to the trunk. 



Just in front of each gonad is a yellowish fat body which in the frog 

 consists of a series of finger-like lobes; it seems to be a fat-storage organ. 

 Above the anterior end of the cloaca is the spleen in which worn-out 

 red blood corpuscles are destroyed and in which white corpuscles are 

 formed. There are also several glands falling under the general designa- 

 tion of ductless glands, the secretions of which are known as internal 

 secretions. Examples of such are the thyroid glands, one of which is 

 situated ventrally on each side in the region of the throat. Others are 

 the thymus glands, which lie below and behind each tympanum, and 

 adrenal bodies, one on the central side of each kidney. 



The tree frogs, or tree toads (Fig. 262), possess dilated adhesive 

 discs upon the toes. Among these types is an interesting tree frog 



