204 REPTILES AND BATRACHIANS 



There is no such thing as green or blue pigments in batra- 

 chians, green being produced by a mixture of black and 

 yellow, blue by the absence of the yellow, the black pigment 

 combining with certain white cells to form the blue colour. 

 R. esculenta presents a very great amount of variation, 

 not only in colour, but also in structure, the length of the 

 limbs and the size and shape of the rudimentary sixth toe, 

 for instance, differing to such an extent as to warrant 

 specific distinction in the eyes of some zoologists. 



The Edible Frog is essentially aquatic, keeping to ponds, 

 slow-running rivers, or ditches, or to their banks, and 

 is, in fact, very seldom found at any distance from water. 

 The male, which is provided with two highly inflatable 

 external vocal sacs, one on each side of the head, behind 

 the angle of the mouth, croaks not only during the breeding 

 season, but throughout the summer months. The eggs, 

 5,000 to 10,000 in number, are similar in shape, but smaller 

 than those of the Common Frog, and are laid in April and 

 May in the south, in June in the north. Unlike those of 

 the common species, they do not float on the surface, but 

 sink to the bottom of the pond. The embryo leaves the 

 e^g with external gills and a well-developed tail, and the 

 tadpole transforms in the late summer. 



As its name implies, this frog is eaten in many parts of 

 Europe, the flesh of its hindquarters being esteemed as a 

 delicacy, and in France, Switzerland, and Italy many 

 people earn a living by frog flshing. According to a 

 recent report in the Bulletin de la Society Nationale d'Accli- 

 matatton, of Paris, the Common Frog is just as frequently 

 brought to market, and just as much appreciated as the 

 Edible Frog. In the price lists of the Paris markets, frogs 

 appear under two categories — grcnouilles de peche and 



