Variation of the Edibfa Frog. 255 



European forms, the course I have followed is surely the 

 belter from a philosophical point of view, whilst the use of a 

 varietal designation precludes all fear of the distinction being- 

 overlooked. 



The following diagram expresses the relationship between 

 the five forms, as I conceive them : — 



Var. lessonte. Var. ehinensis. 



Var. saharica. 



Var. ridibunda. 



We cannot yet apply the tost of crossing experiments 

 in justification of ihe subordinate position assigned to 

 /?. ehinensis, as Pfluger was able, to do in the case of 

 li. esculenta and its var. ridibunda, but another physiological 

 argument has been put forward by Wolterstorff : the large 

 and often sharp-edged metatarsal tubercle of li. ehinensis is 

 an adaptation to burrowing habits unlike those of R. esculenta. 

 We are told that Dr. Kreyenberg observed the Chinese frog 

 to dig and retire deep into the ground of dried-up rice-fields, 

 and this habit is regarded as an important etiological 

 differentiation from its European representatives. Curiously, 

 however, Fejervary very shortly after redescribed the var. 

 lessonce under the name of Wiv.bvlkayi, from specimens living 

 in marshes at the mouth of the Rhone in Switzerland, and 

 observed the behaviour of this frog on land to be different 

 from that of the typical li. esculenta, the large and somewhat 

 movable metatarsal tubercle being used to burrow in the 

 ground after the manner of Pelobates. It is interesting to 

 note, in this connection, that Wolterstorff, who (1906) 

 seemed to attach so great an importance to this peculiarity 

 in the case of the Chinese frog, had (1U04) only reluctantly 

 recognised li. lessona's rank as a variety, a term which for 

 him expresses mere individual variations, such as his colour- 



simple variety de liana esculenta, L., a cles caracteres propres et con- 

 stants qui lui meritent une description particuliere et un nom special ; 

 elle me semble cependant assez voisine de Harm esculenta pour que je 



crois utile de ne Ten point s&parer specinquement Et si, apies 



quelques hesitations, je me decide a classer [JR. ehinensis] comme sous- 

 espece de li. esculenta, e'est par cette seule consideration qu'elle me 

 parait beaucoup plus voisine de cette derniere que de toutes les autres 

 ^renouilles." 



