APPARITION OF SPECIES 103 



of the fact that nearly all the animals and plants of 

 the present day had a very recent beginning in geo 

 logical time, and its disclosure of the disappearance 

 of one form of life after another as we go back in 

 time, till we reach the comparatively few forms of 

 life of the Lower Cambrian, and finally have to rest 

 over the solitary grandeur of Eozoon, oblige it to say 

 that no living thing known to it is self-existent and 

 eternal. 



2. The geological record informs us that the 

 general laws of nature have continued unchanged 

 from the earliest periods to which it relates until the 

 present day. This is the true uniformitarianism 

 of geology, which holds to the dominion of existing 

 causes from the first. But it does not refuse to admit 

 variations in the intensity of these causes from time 

 to time, and cycles of activity and repose, like those 

 that we see on a small scale in the seasons, the occur 

 rence of storms, or the paroxysms of volcanoes. 

 When we find the eyes of the old trilobites to have 

 lenses and tubes similar to those in the eyes of modern 

 crustaceans, we have evidence of the persistence of 

 the laws of light. When we see the structures of 

 Palaeozoic leaves identical with those of our modern 

 forests, we know that the arrangements of the soil, 

 the atmosphere, the sunshine, and the rain were the 

 same at that ancient time as at present. Yet, with 

 all this, we also find evidence that long-continued 

 periods of physical quiescence were followed by great 



