REPRODUCTION 195 



through the transparent membrane which at this stage consti- 

 tutes the egg-capsule. The little one, with the abdomen, 

 tumid with yolk, turned towards the back of the mother, and 

 the limbs folded against the belly, is connected v/ith the 

 membrane by two string-like cords on each side, proceeding 

 from the throat, such as we shall describe presently in some 

 species of Nototvema, and these cords serve to convey the blood, 

 for the purpose of respiration, to the vascular, allantois-like 

 membrane. 



(2) C. b, /3. In the preceding examples, the eggs are simply 

 adherent to the back, leaving shallow hexagonal impressions in 

 the skin. In the well-known Surinam toad, Pipa americana, 

 an inhabitant of the Guianas and Northern Brazil, the eggs 

 are likewise carried on the back of the mother, but the skin 

 thickens and grows round the eggs, until each is enclosed in a 

 dermal cell, which is finally covered by a lid, believed to be 

 formed by a secretion from the glands of the skin. (Plate 

 XVI., A.) The eggs, which may number about 100, and mea- 

 sure five to seven millimetres in diameter, develop entirely within 

 these pouches, and the young leap out in the perfect condition, 

 without even a vestige of a tail. External gills exist but are 

 lost at a very early period, and a long tail is present in the 

 embryo. 



The Pipa is a thoroughly aquatic Batrachian, and pairing 

 of course takes place in the water. The male clasps the female 

 round the waist. The way in which the eggs reach the back 

 of the female has been observed in specimens kept in the 

 London Zoological Gardens. During oviposition the cloaca 

 projects from the vent as a bladder-like pouch, which is 

 directed forwards, between the back of the female and the 

 breast of the male, and by means of this ovipositor the eggs are 

 evenly distributed over the whole back. How the eggs are fer- 

 tilized has not been ascertained. 



(2) C. b. 7. Whilst in the Pipa each egg is enclosed in an 

 outgrowth of the skin of the female's back, in the South 

 American tree-frogs of the genus Nototrema the whole of the 

 brood is sheltered in a common pouch, a structure which, as 

 we have seen, is foreshadowed by the lateral everted fold of 

 Hyla goeldii. This dorsal pouch develops only at the 

 approach of the breeding season, and is evolved by the skin of 



