498 BURMA, ITS PEOPLE AXD PRODUCTIONS. 



or to the ' Oxydactyla,' and in fact tlioy might just as well be referred to the one ris 

 to tlic otlier. Ecsides, the well-known R. macrodou, R. Kuhlii and others liave tiic 

 tips of tlio toes dilated into very distinct disks, much more so tluin several species 

 hitherto referred to Jhjhrana. 



" I have therefore come to the conclusion that, witli regard to the species of this 

 gi-oup, the difference in the shai)e of the tingers and toes cannot be useil as a generic 

 cliarueter, as we should be obliged to place far apart species which in all other 

 respects are very much alike." — Cat. Bat. Sal. p. 7. 



Kow the "difficulty here stated is not one exceptionally encountered among 

 Batrachia, but one which has to be confronted in every department of Zoology, and 

 which must be solved, I think, after a very different fashion to that adopted above, 

 for I cannot tliink that naturalists in general will agree that the fact of an animal 

 possessing a certain mixture of characters, colourably sufficient to allow of its being 

 referred to either of two genera, is a sufficient and a proper ground for uniting these 

 genera, otherwise sufficiently differentiated. There are two courses in such a case, 

 which are preferable to the heroic one advocated in the case of Sana, either by 

 weighing the balance of characters, so as to determine the preponderating value of 

 one set, in a particular direction, or of modifying the characters of the genus, to the 

 extent of meeting the requirements of the species claiming admission therein. 



The development of pneumatic pads, as seen in the typical tree fogs, is, it seems 

 to me, a clear indication of arboreal habits, and, as such, a natural and adequate 

 reason for the at least subgenerio separation of such forms, from those not possessing 

 that character; and it is no valid objection to this view to argue that there are forms, 

 whose claims to be considered as essentially tree or water frogs, are not very clear. 

 JVatura iionfacit sal/um, is the true reply to such an argument. 



There is however, I suspect, one thing which underlies much of this desire to 

 unite veiy dissimilar forms, and that is, a certain confusion wliich has undoubtedly 

 prevailed regarding the dilated extremities of Batracliians. Whilst tree frogs have 

 the extremities of their fingers enlarged into tlisks, which are functionally pneumatic 

 organs of adhesion, other Batrachians, of the most helpless and grovelling Iiabits, have 

 their digits terminally enlarged also ; for example, Callula pulclira : but in this case 

 the enlarged ends are not pneumatic organs, and not improbably subserve the purpose 

 of punching out a cavity in stiff clay, when the animal is desirous of retreating during 

 the dry season into a subterranean burrow. In like manner, the sharp digits of a 

 typical Rana, as R. heradactyla, may be of use to the animal in seizing hold of, and 

 making good its footing in soft mud ; but bo this as it may, the principle seems 

 preferable of endeavouring to follow the indications afforded, regarding the natural 

 habit of the animal, when so clearly given, as in the case of the pneumatic disks 

 of Polypedatea, than to dispense with such aids towards a natural classification — 

 with the result of having to adopt so unnatural an arrangement, as I hold the union 

 of Rana and Pohjpedates, in their typical forms at least, to be. 



Some highly aquatic frogs, Lymnodyfes for example, possess pneumatic pads, 

 which are as much use to them in adhering to slippery rocks or logs, as the same 

 organs arc in enabling arlioreal species to cling to the leaves ; but this is only an 

 additional reason for studying the liabits of a species, if we wish to assign it its 

 proper place in any natural sj-stcm, and tliis aim is altogether frustrated or rendered 

 a work of supererogation, by limiting such a genus as Rana by so arbitrary a character 

 as, free fingerx, regardless of the condition they may present of being either acute, 

 clubbed, or dilated into disks, and regardless, of course, of the co-related habits and 

 mode of life they indicate, be it aquatic, sylvan, subterranean, or arboreal. 



In the following list, those species to which an asterisk (*) is prefixed are un- 

 represented in tlie B.M. Collection. 



E. HEXADACTYLA, Lcss. Nipal. Ccylon. 



Baclyhthra Benyalensis, Less. 

 R. cu/ipora, Dum. et Bib. 

 R. robusta, Blyth. 

 R. vittata, apud Beddome. 



