' CONTENTS 



INTRODUCTION 



PAGE 



I. The Cell Theory . 1 



II. The Recapitulation Theory 3 



III. The Physiology of Development 6 



IV. Embryonic Primordia and the Law of Genetic Restric- 



tion 8 



V. General Characters of Germ-cells 9 



The Spermatozoon 9 



The Ovum 10 



Comparison of the Germ-cells 12 



VI. Polarity and Organization of the Ovum .... 14 



PART I 



THE EARLY DEVELOPMENT TO THE END OF THE 



THIRD DAY 



CHAPTER I. THE EGG 17 



Chemical Composition of the Hen's Egg 20 



Formation of the Egg 21 



Abnormal Eggs 26 



Ovogenesis 2o 



CHAPTER II. THE DEVELOPMENT PRIOR TO LAYING 32 



I. Maturation ^^ 



II. Fertilization '^'^ 



III. Cleavage of the Ovum ^^ 



The Hen's Egg ^^ 



The Pigeon's Egg 43 



IV. Origin of the Periblastic Nuclei, Formation of the 



Germ-wall '^' 



V. Origin of the Ectoderm and Entoderm 52 



CHAPTER III. OUTLINE OF DEVELOPMENT, ORIENTA- 

 TION, CHRONOLOGY 61 



Orientation 



Chronology {Classification of Stages) ^^ 



Tables of the Development of the Chick 68 



V 



IL/^' 



