282 MR. ST. GEORGE MIVART ON ANUROUS BATRACHIANS. [ May 13, 
difference certainly appears at first sight to exist; but if a Frog of 
a somewhat earlier age is examined, it will be seen to be as “ arcife- 
rous”’ asin the Toad. In Mr. Parker’s elaborate Monograph on the 
shoulder-girdle, published by the Ray Society, this fact is well shown 
at plate 5, where the various stages are represented between the 
shoulder-girdle of the Frog-tadpole, ‘‘ with budding limbs but per- 
fect tail’? (fig. 1), and that of the “old male Frog” (fig. 11). In 
the Frog, a few weeks after metamorphosis (fig. 9), the arched car- 
tilages are well shown; and the young Frog with the tail absorbed 
(fig. 6) exhibjts a condition, as regards the overlapping cartilaginous 
arches, closely resembling that presented by the Toad of the first 
summer (fig. 16). 
Now the existence of structures in a rudimentary, transitory con- 
dition during the development of certain animals, does not necessarily 
invalidate the employment of the manifest conspicuous presence of 
such structures in the adult condition of other animals as distin- 
guishing characters of the latter. But in all such cases a really 
marked distinction must be capable of being drawn. This cannot 
be said to be the case in the present instance, where two animals (the 
common Frog and Toad) closely resemble each other after they have 
assumed their final, adult external form. 
The Anura, then, can hardly, I think, be divided into two primary 
sections on the strength of a character so little distinctive as Mr. 
Parker’s observations prove the visible presence of these cartila- 
ginous arches to be. I say visible presence, because even in the 
old male Frog this arch really persists, though its existence is dis- 
guised and hidden by the superficial extension over it of the lower 
part of the coracoid. Some of the other characters are also but 
little satisfactory. Thus the presence of a fontanelle is sometimes 
at least merely a proof of the immaturity of the individual possess- 
ing it. 
“The Anura form such a remarkably homogeneous group, that 
their subdivision is a work of great difficulty, I fully agree with 
Mr. Cope that adaptive modifications should be neglected as affording 
distinctive characters of groups, in favour of others going deeper 
into their essential relations and affinities. But here it is not at all 
evident to me which ave the really essential characters; and when 
these cannot be clearly distinguished, I think it well to turn to such 
others as can easily be observed, though regretting at the same time 
the absence of more significant and satisfactory distinctions. 
Thus the system proposed by Dr. Giinther should, I think, be 
retained as far as possible, being so ‘complete and practically use- 
ful,” as Mr. Cope acknowledges*. 
That Dr. Giinther’s system admits now of some modification, i 
think its author would freely acknowledge. The discovery that some 
species of Callula have very large digital disks, while others are 
totally devoid of such expansions, cannot but cause grave doubts as 
to the propriety of the dividing the Anura into large groups on the 
strength of such a character. ‘Then the presence or absence of a 
* Natural History Review, vol. v. p. 120. 
