AMPHIBIA. 115 



P. Americana is also temporarily provided with trills, \\hich atrophy 

 early. 



The larva of Bhinoderma Darwinii 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 larvse are 

 also stated to be without external gills. 



Amongst the forms with remarkable developments Pseudis paradoxa 

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

 immensely greater bulk than the adult ; a peculiarity which may be simply 

 a question of nutrition, or may perhaps be explained by supposing that the 

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

 existing Frog. 



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 Lophius;' has an underhung 

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

 DO trace of the primordial horny jaws of the ordinary kind. 



b. " 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 chimseroid; it terminates in a 

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

 as compared with that of our ordinary Batrachiau larva?. 



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

 Although most Anurous embryos are not provided with a sufficient 



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 developed. One of these forms, Alytes obstetricaus, belongs to a well- 

 known European genus allied to Pelobates. The 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 



82 



