OF SOUTH CAROLINA. 57 
are as much a part of the nature of a frog as its long legs and aquatic habits. The frog emerging 
from the tadpole state is as much a frog as its parent. Had it appeared with the rudiments of 
wings, we could at once see how it may, in time, become a bird. 
There is, however, some analogy between the succession of fossil fishes and reptiles, and the 
changes that take place during the embryonic development of these animals. Agassiz has 
observed that the changes that take place in the embryo of fishes represent the order in which 
fishes occur in the older fossiliferous rocks. 
The embryo fish is first cartilaginous and heterocircal, from this it passes to the homocircal and 
osseous state. Now we know that the first fishes were heterocircal and cartilaginous, and were 
succeeded by homocircal families. 
Reptiles, too, in the egg, begin with biconcave vertebra, and terminate with the concavo-convex 
articular surfaces, which is the type of living saurians. Now we have seen that the prevailing 
form of the earlier reptilian vertebre was biconcave. These analogies are curious and interesting, 
and afford characters that determine at once the order in the scale of organization that the forms 
thus typified should occupy. As the development in the egg is from lower to higher forms, the 
reptiles with biconcave vertebre, and fishes with heterocircal tails, must stand below the others in 
the seale. But such facts afford not the slightest evidence of the transmutation or self-development 
of species. 
When it is urged that no Naturalist has seen in existing nature any such passage from one 
species to another, the reply is that the time is not sufficient for their observation— the metamor- 
phoses of species proceed so slowly with regard to us, that we can neither perceive their origin, 
their maturity, nor their decay.” But to the organic forms preserved in the solid crust of the earth, 
this want of time cannot apply: with them there was time enough. Let us then see whether any 
evidences of such metamorphoses present themselves. The first organisms belong to the Mollusca 
and Articulata: now if we compare the Brachiopods of that period with the few that exist at the 
present day, we cannot perceive that any progress has taken place in this oldest of families. Ceph- 
alopods have made no advances in organization or numbers, but, on the contrary, almost entirely 
disappeared with the upper part of the Cretaceous systém. Besides, the first of the Cephalopoda 
belonged to the higher and not the lower division of the class. 
The same is true of Reptiles: the Labyrinthodon of the New Red, was far from being the lowest 
of Batrachia. The long period during which the Enaliosaurs peopled the Liassic and Qolite seas, 
presented a good opportunity of observing any transmutation that may have taken place in these 
reptiles. The Ichthyosaurus, for instance, might be expected to lose some of those characters that 
indicate affinity with fishes, and become a Plesiosaurus, but no such change can be observed; on 
the contrary, they were, from the beginning of their existence, contemporaneous, and from the very 
beginning presented the same characters that distinguish them at the last. 
After a profound examination of the reptiles of this period, Prof. Owen comes to the conclusion 
“that the different species of Reptiles were suddenly introduced upon the earth’s surface.” “ Upon 
the whole, they make a progressive approach to the organization of the existing species, yet not by 
an uninterrupted succession of approximating steps.” “But, on the contrary, the modifications of 
osteological structure which characterize the extinct Reptiles, were originally impressed upon them 
15 
