SPECIAL PHYSIOLOGY OF SEX AND REPRODUCTION. 253 



precociously after a very short uterine life, are sheltered in 

 similar, but more developed, pouches of the skin, within which 

 the teats open. 



In oviparous reptiles, the eggs are usually left to hatch of 

 themselves, aided by the warmth of sun and soil. "The 

 female python disposes herself in coils round her eggs, and 

 incubates them for a prolonged period, during which the 

 temperature has been observed to rise as high as 96° F. 

 within the coils." 



Some exceedingly curious parental adaptations occur among 

 amphibians, which seem to have made numerous experiments 



The female Nototre)na niarsupiatuin, — an amphibian, with 

 eggs in a dorsal sac, which is shown partly uncovered. 

 — F'rom Cams Sterne, after Giinther. 



on the matter. Thus in the Surinam toad {Pipa\ the male 

 spreads the ova on the female's back, a sort of erysipelas sets 

 in, and each ovum becomes surrounded by a skin-cavity in which 

 the tadpole develops. After the process is over, the skin of the 

 back is renewed. In other cases this mode of carrying the 

 ova becomes somewhat more definite ; thus in Notodelphys and 

 Nototrema the eggs are stored in dorsal pouches. Nor are the 

 males without their share in the task of parentage. In the 

 obstetric frog {Alytes obstetricajis)^ the male helps to remove 

 the eggs from the female, twists them in strings round his hind 

 legs, and buries himself in the water till the tadpoles escape and 



