372 Dr. Wyman on the Surinam Toad. 
ally much atin was folded against the side and directed towards 
he head. The mouth as in the preceding instances, was not 
terminal, but jenodea a little on the under side of the head. 
When the most advanced ova are compared with those whieh 
had made the least progress, as will be seen by reference to figs. 
2 and 4, which are proportionally magnified representations, it 1s 
ane obvious that in the later periods, the mass of the embryo 
s much greater than that of the yelk and the embryo of the ear- 
tier This increase as shown by weight was found as follows :— 
the embryo represented by fig. 2 weighed 2-95 grains, and that 
by fig. 5, 3°37 grains. It is not improbable that if earlier and 
later periods had been compared, the difference would have been 
sull greater. 
In none of the instances which fell under my notice had the 
final metamorphosis taken place. But Bonnet, Dumeril and oth- 
ers have observed that the tadpole remains in the dermal sac un- 
til its limbs are perfectly formed and the tail has been absorbed, 
until in truth it arrives at the same stage reached by the common 
toad, when having finished its aquatic life to which it is no lon- 
er ada ted, it leaves the ere and seeks its livelihood in a more 
congenial manner on the lat 
Remarks.—In addition to the unusual circumstances under 
which these animals are developed, it will be seen that they are 
objects of especial interest in connection with the general subject 
of the development of Batsachian reptiles. 'The first peculiarity 
which may be noticed is as to the period at which the arms ai 
egs make their appearance. ‘The tadpoles of frogs and toads ac- 
quire a comparatively advanced — of development before any 
traces whatever of limbs are seen ; they leave the egg, cies) of 
sides of the Mbaiinareae ‘The Bg in of the limbs, independ: 
Pa Pairs the vertebral “axis, goes to show rh whatever 
view we may adopt, with regard to the homology of legs, the 
Pest included, they are something superadded to it and not 
volved from it, or any of its processes. I have ascertained by 
direc observation, that even among Frogs, the legs which ap] 
of the tail, in the form of small papille, are prima- 
fily tegumentary growths, that beneath these there 1s developed 
a cartilaginous plate which gradually extends upwards on each 
side until it meets with the transverse processes of the verteb bral 
pe itary with which it becomes permanently connected U 
the form of the pelvis, and at the same time the papillee lee are de- 
