ORIGIN OP THE AMATfiD TRIBES. 



?ion of q tree cut down yesterday. The system of prey 

 amongst animals flourished throughout the whole of the 

 pre-human period ; and the adaptation of all plants and 

 animals to their respective sphere of existence was as 

 perfect in those early ages as it is still. . 



But, as has been observed, the operation of the laws 

 may be modified by conditions. At one early age, if there 

 was any dry land at all, it was perhaps enveloped in an 

 atmosphere unfit for the existence of terrestrial animals, 

 and which had to go through some changes before that 

 condition was altered. In the carbonigenous era, dry land 

 seems to have consisted only of clusters of islands, and 

 the temperature was much above what now obtains at the 

 same places. Volcanic forces, and perhaps also the dis- 

 integrating power, seem to have been on the decrease 

 since the first, or we have at least long enjoyed an exemp- 

 tion from such paroxysms of the former, as appear to have 

 prevailed at the close of the coal formation in England, 

 and throughout the tertiary era. The surface has also 

 undergone a gradual progress by which it has become 

 always more and more variegated, and thereby fitted for 

 the residence of a higher class of animals. 



In pursuing the progress of the development of both 

 plants and animals upon the globe, we have seen an ad- 

 vance in both cases, along the line leading to the higher 

 forms of organization. Among plants we have first sea- 

 weeds, afterward land plants: and among these the sim- 

 pler (cellular and cryptogamic) before the more complex. 

 In the department of zoology, we see zoophytes, radiata, 

 mollusca, articulata, existing for ages before there were 

 aiiy higher forms. The first step forward gives fishes, 

 the humblest class of the vertebrata ; and, moreover, tha 

 earliest fishes partake of the character of the next lowest 

 sub-kingdom, the articulata. Afterward come land ani- 

 mals, of which the first are reptiles, universally allowed 

 to be the type next in advance from fishes, and to be con- 

 nected with these by the links of an insensible gradation. 

 From reptiles we advance to birds, and thence to mam- 

 malia, which are commenced by marsupialia, acknow- 

 ledgedly low forms in their class. That there is thus a 

 progress of some kind, the most superficial glance at the 

 geological history is sufficient to convince us. Indeed 

 the doctrine of the gradation of animal forms has received 

 i remarkable support from the discoveries of this science, 



