168 A Review of the Modern Doctrine of Evolution. | March, 
In order to explain more fully the application of the above 
statements, I introduce a few examples selected from the subjects 
of my studies. Their number might be indefinitely extended. I 
first cite the genera of the tailless Batrachia Anura (frogs, toads, 
etc.), whose relations are very simple and clear, and show the 
parallelism between adult structure and embryonic succession. 
See above, I and 2. 
The greater number of Batrachia Anura fall into two divisions, 
which differ only in the structure of the lower portion of their 
scapular arch, or shoulder girdle. In the one the opposite halves 
are capable of movements which contract or expand the capacity 
of the thorax; in the other the opposite halves abut against 
each other so as to be incapable of movement, thus preserving 
the size of the thoracic cavity. But during the early stages, the 
frogs of this division 
have the movable 
shoulder girdle which 
characterizes those of 
the other division, 
the consolidation con- 
tituting a modification 
superadded in attain- 
ing maturity. Further- 
more, young Anu- 
ra are toothless, and 
one section of the spe- 
cies with embryonic 
shoulder girdle never 
acquire teeth. So here 
we have a group which is imperfect in two points instead of one. 
This is the tribe Bufoniformia; the tribe with teeth and embry- 
onic shoulder girdle is called the Arcifera, and that which is 
advanced in both these respects is the Raniformia. Now the 
frogs of each of these divisions present nearly similar scales of 
development of another part of the skeleton, viz: the bones of 
the top of the skull. We find some in which one of these bones 
(ethraoid) is represented by cartilage only, and the fronto-parietals _ 
and nasals are represented by only a narrow strip of bone each. _ 
In the next type the ethmoid is ossified ; in the next, we have the 
fronto-parietal completely ossified, and the nasals range from nar- 
of Anura. Fi. i 
of the Arciferous 
type ore 
holbrookt). 
Rana tenporaria. 
tadpole with bud- 
ep ty Fig. 3, Fic. 3. 
do. ‘adult. Figs. 2 and 3 from Parker. 
