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best use on a basis of personal observational work by the student in laboratory and field. Without independent personal work of the student little can be learned about animals and their life that will remain fixed. But presentday teachers of biology are too well informed to make a discussion of the methods of their work necessary here. As a matter of fact, the methods of the teacher depend so absolutely on his training and individual initiative that it is not worth while for the authors to point out the place of this book in elementary zoölogical teaching. That the phase of study it attempts to represent should have a place in such teaching is, of course, their firm belief.

The obligations of the authors for the use of certain illustrations are acknowledged in proper place. Where no credit is otherwise given, the drawings have been made by Miss Mary H. Wellman or by Mr. James Carter Beard, and the photographs have been made by the authors or under their direction.

DAVID STARR JORDAN,
VERNON LYMAN KELLOGG.

NOTE. After the pages of the book were cast, it was thought that a transposition of Chapters III and IV would present a more logical arrangement, and teachers are advised to omit in their study scheme Chapter III until Chapter IV is completed.

D. S. J.

V. L. K.

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Birth, growth and development, and death, 78.-Life cycle of

simplest animals, 78.-The egg, 79.-Embryonic and post-em-
bryonic development, 80.-Continuity of development, 83.-De-
velopment after the gastrula stage, 84.-Divergence of develop-

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