CONTENTS. 



PAGE 



Chapter I. — General Conceptions, 17-43 



The Vertebrate Type of Structure, IS 



The Principal Modifications of the Vertebrate Type, 22 



Definition of Anlage, 25 



A Summary of Embryological Development, 25 



Cytomorphosis, . . 27 



Comparison of Larval and Embryonic Types of Development, 32 



Germ-layers 34 



The Relations of Surface to Mass, 37 



The Law of Unequal Growth, 38 



Germ-cells 39 



The Theory of Heredity, 40 



The Law of Recapitulation, 41 



Chapter II. — The Early Development of Mammals, 44-m 



The Spermatozoon, • ... 44 



The Fully Grown Ovum before Maturation, 45 



Ovulation, 46 



The Maturation of the Ovum, 47 



Impregnation of the Ovum, 49 



Segmentation of the Ovum 54 



The Blastodermic Vesicle, 60 



The Embryonic Shield, 62 



Origin of the Mesoderm, 63 



The Primitive Axis 65 



The Notochordal Canal ". 66 



The Notochord, 67 



The Ultimate Fate of the Notochord 68 



The Origin of the Nervous System, 69 



The Structure of the Medullary Canal, 71 



The Early History of the Mesoderm 74 



Somatopleure and Splanchnopleure 76 



The Embryonic Ccelom, 79 



The Mesenchyma, 83 



The Germ-cells, 84 



The Yolk-sac, 85 



The Origin of the Blood-vessels and Blood, 90 



The Blood-corpuscles, . * 93 



The Origin of the Heart 96 



The Germinal Area, 97 



The Main Vessels of the Area Vasculosa 97 



The Ltver, 100 



The Oral and Anal Plates, 100 



The Excretory Organs, 101 



The Allantois, 103 



The Trophoblast, 106 



The Growth of the Embryo, 107 



The Umbilical Cord, . 109 



Chapter III. — The Human Embryo, 1 12-156 



Calculation of the Age of the Human Embryo, 112 



The Classification of the Early Stages, 113 



