Dr. Wyman on the Surinam Toad. 373 
veloped into limbs with their contained bones; thus the pelvis 
which in the adult seems to be an appendage to the vertebral col- 
umn, is in the embryo an ee structure, just as the tooth 
is primarily independent of the ja In this mode of the devel- 
opment of the legs, we havea anieatie analogy to the perma- 
nent constitution of the same parts in Fishes, in which the ven- 
tral fins are never connected with the vertebral column by their 
pelvic bones, these being confined to the abdominal surface of the 
- body. 
The complete development of the tail, adapted to swimming, 
is under the circumstances worthy of attention. In the ordinary 
Ranide the phases of development are in accordance with the pe- 
culiar conditions under which the earlier periods of life are pass- 
ed; their habits are not only wholly aquatic, but they have many 
of the anatomical and physiological sin of fishes, among 
which may be mentioned the existence of branchie, for aquatic 
respiration, and a broad and scien tail for aquatic locomo- 
me on. The embryos of Pipe differ from those of other allied 
ra, in passing through all of theirembryonic phases in closed 
hae sacks, where they neither breathe by the action of aquatic 
currents, nor are capable of executing the ordinary locomotive 
movements ; yet the external branchize are developed, disappear 
and are replaced by internal branchiee, and these in turn by lungs ; 
the tail also acquires its full dev velopment with swimming adapta- 
tions, in the form of muscles and folds’ of skin, as in other tad- 
poles, and after having existed for a certain period, is removed by 
absorption, without having been even once made use of as a lo- 
comotive organ. It appears that in this particular instance the 
exigencies of embryonic life do not require the existence of a 
tail for the purposes of locomotion, and its presence seems to be 
accounted for only on the supposition of the existence of a pre- 
established plan according to which Batrachians generally are 
éveloped, and this plan is adhered to, although the organ may 
Hot be used or not used in the same way as in the. other species, 
It is possible that the materials of the tail serve as a store of nu- 
tritive RPeianess shapee this seems scarcely probable ; but even 
if this be the case, it is none the less a fact that the part assumes 
a “sd the adapatons of which have reference to a function 
wholly differen 
As regards i existence of branchiz, I have observed an anal- 
0gons instance in the embryos of Salamandra gre baie where 
these organs are developed externally, though the eggs are depos- 
i under a log, and the auimal is not aquatic at any hs of 
The only other subject to which it is proposed to refer, is the 
oh of the embryo, by which there is formed at the end of ineu- 
a larger mass than existed in the egg when it commenced, 
Stconp Serius, Vol. XVII, No. 51.—May, 1854. 
