52 THE TESTIMONY OF THE ROCKS. 
and alarm: and it is a curious fact, that in this attitude 
nine-tenth of the Pterichthyes of the Lower Old Red 
Sandstone are to be found.” 
A century has passed since Miller thought he had 
discovered a turtle which was so modified in structure. 
as to be a link between the turtles and the fish. But to 
the present day geology has failed to furnish evidence 
that such a link at one time existed. 
This absence, in the geological record, of transitional 
forms, is one of the greatest difficulties of the evolution- 
istic theory. According to the theory, the fossils found 
in the various layers of rock ought to show gradual 
modifications, linking the various species of animals and 
plants in a finely graduated system, with thousands of 
forms showing in rudimentary structure those organs 
which in the more advanced forms have become fully 
developed. However, no such progress from more to 
less generalized types has been demonstrated, although 
many trained invesfigators have searched the fossiliferous 
rocks for such evidence of evolution. Professor Huxley 
in his “Lay Sermons” admits that an impartial survey of 
the positively ascertained truths of paleontology ‘Either 
shows us no evidence of such modification, or demon- 
strates such modification as has occurred to have been 
very slight; and as to the nature of that modification, it 
yields no evidence whatsoever that the earlier members 
of any long-continued group were more generalized in 
structure than the later ones.” LeConte says: “Although 
the species change greatly, and perhaps many times, in 
passing from the lowest to the highest strata, we do not 
usually, it must be acknowledged, find the gradual transi- 
tions we would naturally expect, if the change were 
effected by gradual transitions.” He further speaks of 
the absence of connecting links as “the greatest of all 
