Variation of the Edible Frog. 253 



the nasal bones are not always so ; there are frequent ex- 

 ceptions, as my own description implies *, but such exceptions 

 occur as well in the var. ridibunda, even in large specimens 

 ( ? from Vienna, 90 mm. from snout to vent, ? from 

 Prague, 120 mm.), and I have come across adults of the 

 var. chinensis in which the nasal bones are completely 

 separated from each other, as is usually the case in immature 

 or small specimens of all the forms. As to the presence or 

 absence of the anterior notch between the frontoparietals, this 

 is a mere individual peculiarity, usually dependent on the 

 size of the specimen; yet I wish to draw attention to the 

 figures given by Camerano f of small specimens of the var. 

 lesson ce from Italy in which the anterior extremity of the 

 frontoparietals answers to Bolkay's definition of JR. chinensis. 



The Size. 



I append the measurements, from snout to vent, of the 

 largest specimens of the different forms in the British 

 Museum. According to Werner J, the var. ridibunda may 

 reach a length of nearly 150 mm. in Austria. 



Var. ridibunda 95 mm. 125 mm. 



Var. saharica 58 80 



F. typica 78 95 



Var. lesson(s 64 78 



Var. chine?isis 70 85 



The Tadpole. 



I have examined large series of tadpoles of the vars. 

 ridibunda and chinensis without succeeding in findino- any 

 characters by which to distinguish them from those of the 

 typical form. The characters pointed out by Annandale§ 

 for the var. chinensis are.not confirmed as regards the mouth- 

 disc, the position of the spiraculum, or the length of the tail 

 compared to that of the body. 



Conclusions. 



When dealing with polymorphic species, botanists often 

 distinguish between forms (species, some term them) of first, 

 second, third, and fourth rank. Applying this concept to 

 Rana esculenta, the typical form representing of course the 



* Taill. Batr. Eur. p. 279. 

 t Mem. Ace. Torin. (2) xxxv. 1883, p. GO. 

 % Kept. Amph. Oesterr.-Uiig. p. 88 (1897). 

 § Mem. As. Soc. Beng. vi. 1917, p. 147. 



