96 



INTRODUCTION. 



Fig. 40. 



The annexed figure (40) of the vertebral column 

 (ventral aspect) of a recently transformed Pelobates 

 cidtripes shows well the independence of the inter- 

 vertebral spheres and the three elements which enter 

 into the formation of the urostyle. 



A glance at this figure will also 

 show to what extenb the importance 

 of the mode of articulation of the 

 vertebras has been overrated by those 

 systematists who have proposed to 

 divide the tailless Batrachians pri- 

 marily into procoelian and opistho- 

 coelian types. As a matter of fact, 

 both occur in the family Pelobatirfae, 

 some of the exotic genera of which 

 are normally opisthoccelian. 



During larval life the habits vary 

 considerably according to the species. 

 Thus Hyla is always on the move, 

 swimming about in every direction like a fish ; Bom- 

 binator, Alytes, Pelobates, and liana keep more to 

 the bottom, approaching the borders of the ponds 

 or pools during the hotter part of the day to sun 

 themselves in shallow water ; Discoglossus, Pelodytes, 

 and Bufo are in the habit of coming frequently to 

 take air on the surface, where they swim about with 

 upturned bellies. 



The notion that tadpoles are exclusively herbivorous 

 has long been exploded ; they feed on both vegetable 

 and animal substances, and usually show a preference 

 for the latter, in addition to the microscopical organ- 

 isms contained in the ooze, which they swallow in large 

 quantities. Their carnivorous or even cannibal habits 

 are only too noticeable in confinement, and they have 

 been utilised for making small and delicate skeletons. 

 The tadpoles of Bombmator and Alytes are almost 

 exclusively carnivorous, the real difference between 

 them and the perfect animal being that the former 

 feed readily on dead or even decomposing matter, 



