264 ANURA CHAP. 



spotted with black and white or yellow, in opposition to the 

 R. temporaria group, where these parts are never spotted. 



The total length of this species varies much. Specimens 2^ 

 inches in* length are certainly mature, those of 4 inches are 

 unusually large, and Boulenger has received a giant from 

 Damascus, which measured 125 mm., or nearly 5 inches. The 

 females are larger than the males. 



The variations in colour are not only local but also in- 

 dividual, moreover the colours are changeable. The ground-tint 

 ranges from dull brown through olive to bright green, the dark 

 spots being more or less pronounced and numerous ; the light 

 vertebral line is olive-yellowish, bright green, or altogether absent. 



Those which inhabit waters with plentiful vegetation, like 

 water-lilies and other luxuriant plants, are generally prettier and 

 more vividly coloured than those which live in swamps and 

 ponds with dark mud, or where the prevailing vegetation has 

 a sombre aspect. Cold and dull, warm and sunny days also 

 influence the water-frogs, and those which have been kept in a 

 dark tank look very different from the bright assembly which 

 had been put in some weeks before. 



Various attempts have been made at subdividing It. esculenta 

 of Linnaeus into sub-species, and Boulenger has now, after the 

 attentive study of an enormous material, arranged them in four 

 principal and recognisable races. The chief differences are the 

 relative length of the femur to the tibia and the size of the 

 metatarsal tubercles. 



1. Var. ridibunda, Pallas. The right and left heels overlap 

 each other when the thighs are stretched out at right angles to 

 the vertebral column, and the tibia is closely folded up against 

 the thighs. When stretched forwards, the heel reaches the eye 

 or even the tip of the snout. The inner metatarsal tubercle is 

 feebly developed, very small and blunt ; the outer tubercle is 

 absent. 



That part of the thighs which is concealed by the legs when 

 the animal is at rest is whitish or pale greenish, marbled with 

 dark olive, or bronze, or of the latter colour with or without 

 small light spots. No trace of yellow is ever to be detected 

 on that region, nor at the axillae or on the groin. The vocal 

 sacs are strongly pigmented with black, when inflated they are 

 pale grey. The iris is a mixture of black and gold. 



