CONTENTS 15 



CHAPTER XL 



PAGE 



Wildlife Conservation (By Walter P. Taylor) ____----- 78-1 

 The Abundance of Wild Animals, 784; The Natural Range of Wild 

 Animals, 789; The Coming of Civilization and a Declaration of Inde- 

 fensibles, 792; The Problem of Restoration, 794. 



CHAPTER XLI 

 Comparative Embryology (By A. Richards) _____-__- 798 



CHAPTER XLII 



MAMMALLA.N DEVELOPMENT __________--_-- 812 



Organs and Systems, 817. 



CHAPTER XLIII 



Genetics and Eugenics (By Frank G. Brooks) ______-- 821 



The History of a Great Discovery, 821; Mendel's Law, 821; 

 Derivatives of Mendel's Law, 823; The Physical Basis, 824; Plotting 

 Crosses, 825; Complications of Mendelian Inheritance, 827; Inheritance 

 of Sex, 831; Linkage, 832; Sex Linkage, 832; Crossing Over, 834; 

 Mutations, 836; Human Heredity, 836; Matings Among Defectives, 

 839; The Differential Birth Rate, 839; Family Size in Eugenic 

 Groups, 841; Family Size in Dysgenic Groups, 842; What Can Be 

 Done? 844; Some Eugenic Measures, 844. 



CHAPTER XLIV 



Animal Behavior (By Ina Cox Gardner) ____-_---- 846 

 Introduction, 846 ; Tropistic Behavior, 849 ; Reflex Behavior, 850 ; 

 Chain Reflex Behavior, 851; Habitual Behavior, 852. 



CHAPTER XLV 

 Paleontology (By W. M. Winton) _______----- 854 



CHAPTER XLVI 



Phylogenetic Relations op Animal Groups and the Theory of Evo- 

 lution _____-___-------- 863 



Colony Formation in Certain Protozoa, 864; Development of the Gas- 

 trula, 865; Trochophore Larva, 865; Peripatus and the Wormlike 

 Ancestry of Arthropoda, 865; Eehinoderms and Their Larval Rela- 

 tions, 866; Ancestry of the Vertebrates, 866; Basis for the Theory 

 of Evolution, 870; Darwin and Studies of Evolution, 885, 



