292 FROGS, TOADS, AND NEWTS [CH. VIII 



tioning first as male and subsequently as female. The 

 eggs produced give rise to embryos which escape from 

 the alimentary canal of the frog in the faeces and become 

 the free-living form. 



OTHER BRITISH AMPHIBIA. 

 Anura (Tailless Amphibians). 



(1) The Edible Frog, Rana esculenta, has occasionally 

 been found in England. It is not really indigenous but 

 probably in all cases has been introduced. Some sixty 

 years ago large numbers of this species and quantities 

 of spawn were imported from the Continent and put down 

 in the fen district. At one time they were abundant 

 in Fowlmere Fen, Cambs. This species is larger than 

 R. temporaria and greener in general colour; it has not 

 a black mark from the eye to the shoulder, while down 

 the middle of the back are three lines, one median and 

 two lateral, by which it may readily be distinguished. 

 The eyes are closer together, the intervening space more 

 convex, the tympanic membrane larger, and the hind 

 limbs relatively longer than in our native species. The 

 male possesses a pair of large pouches, the vocal sacs, 

 communicating with the cavity of the mouth and placed 

 one on each side of the head ventral to the tympanic 

 membrane ; they are about the size of a large pea seed. 

 The edible frog is more strictly aquatic than the common 

 species and does not wander so far from the water. 



(2) The Common Toad, Bufo vulgaris, is more brown 

 and duller in colour than the frog. The skin is covered 





