INTRODUCTION. 



probably expecting to find in it the rubeta of older writers^ adds 



that it ' ist fur giftig- zu halten/ 



Leeiiwenhoek ^ also correctly distinguished between them, but it 

 is to RoseF that we are chiefly indebted for a careful discrimination 

 and an accurate knowledge of the life-histories of the two species. 



Fig. I. 



The green water-frog, Rana esculenta L. 



Rana esculenta, L. The green water-frog, Fig. i, usually attains 

 a larger size ^ and is more active than the other species, and for this 



* Leeuwenhoek, Arcana Naturse.Vol. Ill of Ecker's edition. Leyden, 1722. Epist . 65 

 ad Reg. See. Lond., p. 154. 



^ Eosel, Naturgeschichte der Frosclie Deutsclilands, ed. Schreber. Niirnberg, 1815, 

 p. 36. 



^ The extreme sizes are much more pronounced in this species. I have never found 

 R. temporaria of the size attained by large specimens of the water-frog. 



