AMPHIBIA. 115 



P. Americana is also temporarily provided with gills,' which atrojjhy 

 early. 



The larva ol' Rhinoderma Dai-winii is stated by Jiminez de la Espada 

 to be without external gills, and it appears to be hatched while still in the 

 laryngeal pouch of the male. In Nototrema marsupiatum the larvae are 

 also stated to be without external gills. 



Amongst the forms with remarkable developments Pseiidis paradoxa 

 deserves especial mention, in that the tadpole of this form attains an 

 immensely greater bulk than tbe adult ; a peculiarity which mav be simply 

 a question of nuti'ition, or may perhaps be explained by supposing that the 

 larva resembles a real ancestral form, which was much larger than the 

 existing Fi'og. 



Another form of perhaps still greater morphological interest is the 

 larva of Dactylethra. The chief peculiarities of this larva (fig. 83) have 

 been summarized by Parker (No. 107, p. 626), from "whom I quote the 

 following passage : 



Fig. 83. Larva of Dactylethra. (After Parker.) 



a. " The mouth is not inferior in position, suctorial and small, but is 

 very wide like that of the ' Siluroids and Lophiiis;' has an underhung 

 lower jaw, an immensely long tentacle from each upper lip, and possesses 

 no trace of the primordial horny jaws of the ordinary kind. 



h. " In conformity with these characters the head is extremely flat or 

 depressed, instead of being high and thick. 



c. " There are no claspers beneath the chin. 



d. " The branchial orifice is not confined to the left side, but exists on 

 the right side also. 



e. " The tail, like the skull, is remarkably chimasroid; it terminates in a 

 long thin pointed lash, and the whole caudal region is narrow and elongated 

 as compared with that of our ordinary Batrachian larvae. 



f. " The fore-limbs are not hidden beneath the opercular fold." 

 Although most Anurous embrj'os are not provided with a suflScient 



amount of yolk to give rise to a yolk-sack as an external appendage of the 

 embryo, yet in some forms a yolk-sack, nearly as large as that of Teleostei, 

 is develoi)ed. One of these forms, Alytes obstetricans, belongs to a well- 

 known European genus allied to Pelobates. Tlie embryos of Pipa dorsigera 

 (Parker) are also provided with a very large yolk-sack, round which they 

 are coiled like a Teleostean embryo, A large yolk-sack is also developed 

 in the embryo of Pseudophryne australis. 



The actual complexity of the organization of different tadpoles, and 

 their relative size, as compared with the adult, vary considerably. The 



8—2 



