PALAEONTOLOGY AND GEOLOGY 



mal and vegetable forms, and the enormous lapse 

 of time indicated by the accumulation of fossil if erous 

 strata, the only circumstance to be wondered at is, not 

 that the changes of life, as exhibited by positive evi- 

 dence, have been so great, but that they have been so 

 small. Bearing these opinions of Huxley in mind, it is 

 surprising, to say the least, to find that this passionate 

 advocate of rigorous scientific thinking preached, at 

 the same time, the established certainty of evolution, 

 not only in its broad outlines but also tracing its 

 course in minute detail and teaching that natural se- 

 lection was its cause and method. 



We have, of course, since Huxley's time, increased 

 our accumulations of fossils and have filled in some 

 of the imperfections of the palaeontological record, 

 but in essentials we are in the same state of uncer- 

 tainty. I have made a selection of some of the most 

 important breaks in our present record, and the reader 

 may refer to the end of the chapter for a table of the 

 geological periods. The material has been abstracted 

 from Chamberlain and Salisbury's Geology. 



The duration of the Archaeozoic and Proterozoic 

 ages is estimated to be much longer than all the later 

 ages taken together. Fossil remains are found only 

 in the upper Proterozoic strata and are at best rare 

 and poorly preserved. 



Abundant fossils of trilobites and other shell-fish 

 are first found in the Cambrian sedimentary rocks of 

 the Palaeozoic age. These animals were quite com- 



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