Geology and Natural History. 77 



Laboratory Directions in Principles of Animal Biology; by A. 

 Franklin Shull, with the collaboration of George R. Larue 

 and Alexander G. Ruthven, and Peter 0. Okkelberg. Pp. 

 ix, 81. New York. 1919 (McGraw-Hill Book Company).— 

 Although teachers of introductory courses in biology have long 

 since abandoned the old type system of Huxley in their lectures 

 and recitations, many have not deemed this practicable in the 

 laboratory exercises which constitute an important part of the 

 study. Consequently there often arises an unfortunate lack of 

 harmony between the classroom and the laboratory. That it is 

 possible to avoid this, and to conduct classes in biology exactly 

 as is done in chemistry and physics ; namely, to make the class- 

 room and laboratory work of each day mutually complementary, 

 many teachers have already discovered. And if any doubt still 

 exists in the minds of some, it should be dispelled by these com- 

 panion books, the outcome of practical experience in large ele- 

 mentary classes. Only in exceptional cases will it be necessary 

 to dissociate the classroom and laboratory topics and no import- 

 ant branch of biology needs to be omitted. 



The course presented begins with a brief historical introduc- 

 tion, and leads through the morphology and physiology of the 

 cell to cellular differentiation, morphology and physiology of 

 organs, reproduction and breeding habits ; embryology ; genetics ; 

 taxonomy; ecology; zoogeography; paleontology; and evolution. 



This text-book in the hands of a capable and enthusiastic 

 teacher will lead the student consistently from the elementary 

 principles of living matter to the profound conceptions of his own 

 position in the living world and his relationship with, and 

 dependence upon, his fellow organisms. To the general reader the 

 book will give a comprehensive survey of the field of animal biol- 

 ogy as it has been developed in recent years. To such the excel- 

 lent illustrations will take the place of the laboratory study, and 

 a glossary of unusual merit will supply the meaning of all the 

 technical terms which the book contains. w. r. c. 



6. Cytology; with Special Reference to the Metazoan 

 Nucleus; by W. E. Agar. Pp. xii, 224; with 91 text-figures. 

 London, 1920 ( (Macmillan & Company). — The search for the 

 mechanism of inheritance has been carried on with great zeal in 

 recent years, and although there are still many details not fully 

 understood, the essential features of the hereditary apparatus 

 have apparently been discovered. While the chromatin of the 

 nucleus is looked upon as the direct agent in heredity, all the 

 parts of the cell are so intimately related and mutually depen- 

 dent that an understanding of the whole is necessary for a clear 

 conception of any part. This book is, therefore, essentially a 

 summary of our present knowledge in regard to the structure of 

 the metazoan cell and the various modifications and manifesta- 

 tions of the cell organs, but the principal emphasis is naturally 

 placed on the chromosomes as the physical basis of heredity. 



