BOOKS BY PROFESSOR GROOS. 

 The Play of Man. 



By KARL GROOS, Professor of Philosophy in the Uni- 

 versity of Basel. Translated, with the author's coopera- 

 tion, by Elizabeth L. Baldwin, and edited, with a Preface 

 and Appendix, by Prof. J. Mark Baldwin, of Princeton 

 University. 121110. Cloth, $1.50 net; postage, 12 cents 

 additional. 



" A book for parents to read and ponder over with care and mental 

 diligence. " Chicago Tribune. 



" Not alone does the .work make an appeal to the strictly scientific. 

 The general reader will find in it absorbingly interesting facts, pre- 

 sented in a way which may prove of practical use." Boston Advertiser. 



" A very valuable book. The results of Professor Groos's original 

 and acute investigations will be especially appreciated by those who are 

 interested in psychology and sociology, and they are of great impor- 

 tance to educators." Brooklyn Standard Union. 



The Play of Animals. 



By KARL GROOS. Translated, with the author's co- 

 operation, by Elizabeth L. Baldwin, and edited, with a 

 Preface and Appendix, by Prof. J Mark Baldwin, of 

 Princeton University. i2mo. Cloth, $1.75. 



" A work of exceptional interest to the student." San Francisco 

 Argonaut. 



" His work is intensely interesting. Both nature and books have 

 been ransacked for materials, and the selection shows a trained intelli- 

 gence of the highest order in observation and acumen." The Inde- 

 pendent. 



D. APPLETON AND COMPANY, NEW YORK. 



