TAILED BATKACHIANS AND FROG BATRACHIANS. 13] 



of Amphibia, the Frog Batrachians (Batrachia, or Anura), 

 is yet more complete than in the Salamanders. To these 

 belong all the various kinds of Toads, Water-frogs, Tree- 

 frogs, etc. In the course of transformation these lose not 

 only the gills, but also the tail, which drops off in some 

 cases earlier, in others later. In this respect the various 

 species differ somewhat from one another. In most Frog 

 Batrachians the larvae drop the tail very early, and the 

 tail-less frog-like form subsequently grows considerably 

 larger. Other species, on the contrary, as, for instance, the 

 Pseudesparadoxus of Brazil, as also an European Toad (Pelo- 

 batesfuscus) remain for a very long time in the fish form, 

 and retain a lengthy tail till they have almost attained 

 their full size; hence, after their metamorphosis is com- 

 pleted, they appear much smaller than before. The opposite 

 extreme is seen in some Frogs but recently brought under 

 notice, which have lost the whole of their historic meta- 

 morphoses, and in which no tailed and gilled larva emerges 

 from the egg, but the perfect Frog, without tail or gills. 

 These Frogs inhabit isolated oceanic islands, the climate 

 of which is very dry, and which are often for a con- 

 siderable length of time without fresh water. As fresh 

 water is indispensable for gill-respiring tadpoles, these Frogs 

 have adapted themselves to this local deficiency and have 

 entirely relinquished their original metamorphosis, e.g., 

 Hylodes martinicensis. 158 



The ontogenetic loss of gills and tail in Frogs and Toads 

 can of course only be phylogenetically explained as owing 

 to the fact that these animals have descended from long- 

 tailed salamander-like Amphibians. This is also proved 

 beyond doubt by the Comparative Anatomy of the twc 



