THE TESTIMONY OF THE ROCKS. 59 
pressions as the following abound: “Where direct pale- 
ontological observation has ascertained in particular 
cases the steps of progress in the development of organs, 
as, for example, those of the teeth in Mammals, the 
facts become a basis for further use in the same direction.” 
(p. 402.) “The grander divisions of geological time 
should be based, in a comprehensive way, on organic 
progress” (from simple to more complex structures) (p. 
404.) “When the relations of the beds to those recog- 
nized in other regions have been ascertained through 
fossius2a.. “7p. 4059) 
The principle announced by Dana is accepted by geo- 
logists generally. Angelo Heilprin in “The Earth and 
its Story,’ p. 153 ff. has the following: “There has been 
a steady and progressive advance in the general type of 
organization from the oldest to the newest periods; more 
highly developed or more complicated forms have succes- 
sively replaced forms of simpler construction; and this 
advance is still continuing to-day. Once more, the cor- 
rectness of the evolutionary hypothesis is taken for 
granted. In the oldest rocks, for example, no trace of 
backboned animals has yet been detected; when such do 
appear for the first time, they show themselves in their 
lowest types, the fishes; these are succeeded later by the 
amphibians( frogs, newts, salamanders), and these again 
by reptiles. And if we take the fishes by themselves, we 
find that they, too, begin with their lower, if not abso- 
lutely the lowest types, and progressively develop their 
higher ones. This history is repeated in the cases of 
the reptiles and quadrupeds—in fact, with every class of 
animals that is known to us. Naturalists (evolutionists ) 
are to-day well agreed among themselves that all ani- 
mal and vegetable forms are derivatives from forms 
that preceded them. .... Hence it is, that, in following 
