276 GEOLOGY. 



of these figures is to give emphasis to the fact that the period was one 

 of great duration. 



THE LIFE OF THE CAMBRIAN. 



Perhaps no single event in the history of the earth possesses greater 

 interest than the first appearance of life. We have already learned 

 that the real advent of life on the globe has not been revealed by the 

 record, as thus far known, and there is almost no hope that it ever will 

 be. There is good evidence that life existed in the several great periods 

 of the Proterozoic, and in some at least of those of the Archeozoic. 

 Under the accretion hypothesis, it is not improbable that the real 

 beginning of life on the earth greatly antedated even the oldest of the 

 accessible Archean formations. If so, it is quite beyond hope that 

 the great problem of the earliest forms of life will ever be solved by 

 direct fossil evidence. Even in the Archeozoic and Proterozoic the 

 evidences of life, while sufficient to create a firm conviction that the 

 earth was then tenanted by living things, are so indirect or obscure 

 that they give very little idea of the nature of the life. Such little 

 information as the imperfect fossils give, carries in itself evidence that 

 it does not tell the whole story, or even the main part of it, for the 

 life imperfectly represented could not have lived without other forms 

 of life which are not represented. 



The first fair record. — In the Cambrian, for the first time, there is a 

 fair preservation, in fossil form, of the life of the period. Even here 

 the record is very far from complete, but it is an immeasurable advance 

 on the records of previous periods. Something of the interest and 

 importance that would have attached to the earliest forms of life, had 

 they been preserved, is therefore transferred to this first legible record. 

 Preliminary to a review of this record, the chief ways in which it bears 

 on questions of fundamental interest may receive a moment's con- 

 sideration. 



What stage of evolution is represented? — Foremost among the 

 questions that arise is the stage of development that had been already 

 attained by life, when thus first fairly preserved. Was the life really 

 primitive, implying that it was not far removed from the true first 

 forms of life, or did it bear signs of great previous evolution? 



The stage of evolution attained may be estimated (1) by the degree 



