480 TEXTBOOK OF ZOOLOGY 



The marsupial frogs of South America, Gastrotheca, carry their 

 eggs in a dorsal sac or brood pouch which is found in the female. 

 The Amazonian frogs Pipa and Protopipa carry their eggs and tad- 

 poles in individual dermal chambers on the back of the female. In 

 the ease of a small frog (Bhinoderma) in Chile, eggs are carried in 

 the vocal pouch of the male where they metamorphose and hatch as 

 fully formed young. Phyllolates and Dendrobates, two frogs from 

 the northern part of South America and Central America, transport 

 their tadpoles on the back of the male to the stream where they 

 pass the rest of their tadpole stage and metamorphose. In the case 

 of the obstetrical toad of Europe (Alytes olstetricans), the male 

 carries the eggs wrapped around his legs until they hatch. 



Fig. 264. — Adult Ambystoma tigrinunij tiger salamander. (Photograph by Sanders.) 



Secondary Sexual Characters. — Secondary sexual characters com- 

 pose those differences, exclusive of the reproductive organs, be- 

 tween males and females of a species. These differences may be 

 both structural and physiological. Familiar secondary sexual char- 

 acters are the nuptial pads of male frogs, their swollen thumbs 

 during the breeding season, and, in the male bullfrog, the size of 

 the tympanum, which is larger than that of the female. These 

 sexual characters may be various. In some salamanders the teeth 

 of the male may elongate; in others, glandular masses at the base 

 of the tail or elsewhere may be present in the males and absent in 

 the females. One of the most bizarre secondary sexual characters 

 is found in an African frog (Petropedetes newtoni). In this frog 

 the male has the columella of the ear pushed through the drum to 

 form a noticeable projection. 



Hibernation. — ^Amphibia are more or less adapted to their en- 

 vironment; and, when winter comes, bringing low temperatures and 



