IKE VB AS 
Geological Biology, an Introduction to the Geological History of 
Organisms. By H.S. Wiriiams. Henry Holt & Co., 1895. 
Or late years numerous books on evolution have appeared, but per- 
haps none have been more practical or suggestive in their treatment of 
the subject than the present volume by Professor Williams. The 
subject matter of the book was originally presented in the form of 
lectures, delivered first at Cornell University and later at Yale. These 
lectures were intended to supplement a laboratory course in paleontol- 
ogy, by suggesting the most vital lines of thought in the actual inter- 
pretation of fossils considered as the records of the history of 
organisms. Inthe preparation of the matter for publication the lecture 
form has been dropped and the material so revised as to serve the 
general reader as well as the student. ‘ 
It is evident that the biologist proper, who deals alone with con- 
temporaneous organisms, must rest with a theoretical interpretation of 
the laws of evolution. The actual records of the history of organisms 
are found in the fossils preserved in the rocks and it is the purpose of 
the author to point out the chief facts and factors of evolution as shown 
from a study of the fossils. 
In beginning the study of any history some system of chronology 
must be adopted. In the early chapters of the book the author dis- 
cusses the development of the geological time-scale as now generally 
adopted, passing from the earliest classification of rocks based on their 
original order of formation, through the second stage in which the 
classification was based on their mineral constituents, to the present 
classification based on their fossil contents. 
Fossils represent the hard parts of living organisms, or those parts 
which have attained definite and fixed form during the life of the 
organism. “The history of organisms, which we particularly trace in the 
study of fossils, is not the history of imperfect organisms struggling 
towards perfection, but it is the history, for each age and epoch, of the 
perfected adjustment of the organisms of the time to the particular 
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