260 THE DOCTRINE OF DESCENT. 
physiological ascent, linked with various morphological 
transformations, which may similarly be shown between 
the ancient and modern specimens of the Labyrintho- 
donts. The Batrachians, indeed, rise higher in develop- 
ment than the Ceecilia; but, as the friend above men- 
tioned informs me, they more nearly approach the 
Myxine in the construction of the internal gills of their. 
larva. We shall obtain a general view of the reptiles 
by means of the appended diagram, in which we shall 
avoid any minute systematic designations. 
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