188 Kepoet of the State Geologist. 



which effect the separation of carbon from the bodies with which 

 it is combined are carried on in living organisms. Carbon, in all 

 its forms, except perhaps the diamond, results always from the 

 modification of materials of organic origin. It is then possible 

 that the carbon and the carburets of the Precambrian deposits 

 represent all that remains of that ancestral fauna whose exist- 

 ence is proved by the most simple process of reasoning. 



It remains now to explain how it happens that no relics of 

 those primitive organisms have remained to our day. It is 

 because the deposits of that epoch, once formed, were subjected 

 to great modifications, both mechanical and chemical, which 

 constitute the process of metamorphism. The sedimentary lay- 

 ers were pierced with eruptive rocks, among others granite, 

 which spread over them or extended under them and filled their 

 interstices. Either by direct contact or more frequently by the 

 action of water superheated and charged with salts in solution, 

 the sedimentary rocks underwent a sort of baking, which devel- 

 oped numerous minerals not before existing therein, and which 

 sometimes give to them the appearance of eruptive rocks. It is 

 easy to understand how the schists thus metamorphosed pre- 

 served no traces of the fossils they may have contained. 



A purely mechanical overturn also sometimes suffices to make 

 the discovery of fossils impossible. Thus M. Gaudry tells us 

 that the English geologists, Sedgwick and Murchison, explored 

 the Cambrian beds for a long time without discovering fossils. 

 They observed that almost every part of the rock was fissured 

 or at least cracked perpendicular to the direction of the stratifi- 

 cation. In examining places where, on the contrary, the cracks 

 were parallel with this direction, they found numerous fossils 

 well preserved. We should not give up the hope that at some 

 future time geologists may succeed in finding in the Precambrian 

 layers places where metamorphism has not made itself felt. 

 Until that time arrives we can draw no conclusions from geologic 

 data concerning the origin of life, and we must content our- 

 selves with the theories which embryogenic and comparative 

 studies furnish. 



In conclusion, it is seen that the study of the filiation of organ- 

 isms rests on methods the precision of which increases with the 

 increase of our^ knowledge of the laws of evolution. These 



