682 THE AMERICAN NATURALIST. 
and Acérata; Scudder, the Insecta. A few chapters, notably those 
on the: Molluscoidea, Mollusca, and Trilobita, are entirely rewritten. 
Science text-books are proverbially behind the advances of the 
sciences they represent. In general this conservatism is not without 
compensation, since no single author of a comprehensive treatise can 
judge of the value of new discoveries or adopt innovations until they 
have stood the test of time and become incorporated into the stand- 
ard body of scientific literature. Much of this danger has been obvi- 
ated by the codperation of men of recognized authority in special 
branches and by their restraint in following along prescribed lines. 
The result of this coóperation, as in the present volume, is a com- 
posite work. Instead of a compilation from various authorities, each 
chapter bears its own authority, and as such the book will have a 
standing and usefulness among advanced students it would not other- 
wise attain. CE RÀ 
