190 THE ANATOMY OF VEETEBEATED ANIMALS. 



urinary duct, which lies on the outer side of the kidney, 

 ends blindly in front, and opens behind into the cloaca. 

 The urinif erous tubuli also pass directly from the outer mar- 

 gin of the kidneys into the genito-uriuary duct. In the 

 Bafrachia there is likewise a genito-urinary duct, and the 

 vasa efferentia run to the inner edge of the kidney and 

 enter it. In Bombinator igneus and Discoglossus pidus, the 

 genito-urinary duct receives the urinary products and the 

 spermatozoa, in the same way as in the Urodela. But, in the 

 Frogs and Toads, the urinary tubuli are gathered together 

 into a special small canal which opens into the genito-urinary 

 duct near its termination in the cloaca, and the vasa effe- 

 rentia pour their contents into this canal. Under these 

 circumstances, the part of the genito-urinary duct which 

 lies beyond the renal canal may become obliterated, as in 

 the Frogs ; or may persist, and play the part of a vesicula semi- 

 nalis, as in the Toads. 



In the female Amphibia, the kidneys have, as in the male 

 Frogs and Toads, a renal canal which opens into the lower 

 part of the oviduct. 



It would appear from these facts that the oviduct in the 

 female, and the genito-urinary ducts in the male, Ampliibia 

 represent both the Wolffian and the Miillerian ducts of the 

 higher Vertehrata. 



In most Amphibia the ova are impregnated and hatched 

 outside the body, but internal impregnation and incubation 

 occur in some of the Urodela. In Pipa the eggs are hatched 

 in pouches of the dorsal integument, while the male Alytes 

 carries them twisted in strings round his legs. 



When hatched, the young are devoid of respiratory organs 

 and of limbs, and are provided with a long tail, by means 

 of which they swim about. Branchial clefts soon make their 

 appearance; and ciliated external branchial plumes, like those 

 of the perennibranchiate Urodela, are developed. A pair of 

 suckers are sometimes formed upon the under-surface of 

 the mandibular region, and the jaws acquire horny sheaths. 



A broad opercular membrane is developed in front of the 



