DISCOVERIES WITH SACRED HISTORY. 31 
the many extinct fossil forms of animal life 
succeeded one another upon the early surface of 
the globe : this evidence consists in the petrified 
remains of eyes of animals, found in geological 
formations of various ages. In a future chapter 
I shall show, that the eyes of Trilobites, which 
are preserved in strata of the transition forma- 
tion, (PI. 45, Figs. 9, 10, 11), were constructed 
in a manner so closely resembling those of ex- 
isting Crustacea ; and that the eyes of Ichthyo- 
sauri, in the lias, (PI. 10, Figs. 1, 2), contained 
an apparatus, so like one in the eyes of many 
birds, as to leave no doubt that these fossil eyes 
were optical instruments, calculated to receive, in 
the same manner, impressions of the same light, 
which conveys the perception of sight to living- 
animals. This conclusion is further confirmed 
by the general fact, that the heads of all fossil 
fishes and fossil reptiles, in every geological for- 
mation, are furnished with cavities for the re- 
ception of eyes, and with perforations for the 
passage of optic nerves, although the cases are 
rare, in which any part of the eye itself has been 
preserved. The influence of light is also so 
necessary to the growth of existing vegetables, 
that we cannot but infer, that it was equally 
essential to the development of the numerous 
fossil species of the vegetable kingdom, which 
are coextensive and coeval with the remains of 
fossil animals. 
