OUTLINES OF 

 CHORD ATE DEVELOPMENT 



CHAPTER I 

 THE DEVELOPMENT OF AMPHIOXUS 



PAGE 



INTRODUCTION . ..... 2 



I. THE GERM CELLS AND THEIR PRODUCTION . . . . ... 4 



II. THE EMBRYONIC PERIOD . 



A. FHOM FERTILIZATION TO THE TIME OF HATCHING ... 9 



1. Fertilization 9 



2. Cleavage 11 



3. Gastrulation 15 



4. The Formation of the Central Nervous System .... 20 



5. The Formation of the Notochord 23 



6. The Formation of the Mesoderm and Enter ocoels ... 24 



B. FROM HATCHING TO THE FORMATION OF THE MOUTH . 27 



1. The Central Nervous System 27 



2. The Notochord 28 



3. The Mesodermal Somites and Ccelom 29 



4. The Enter on and Its Appendages 33 



III. THE LARVAL PERIOD ....... . . ....."... 37 



1. The Central Nervous System 37 



2. The Gill Slits , . . . 39 



3. The Club-shaped Gland 43 



4. The Endostyle . . "j, '.'.... 43 



5. The Mouth and Associated Structures 44 



6. The Preoral Pit and Its Derivatives . 44 



7. The Blood-vessels 46 



8. The Atrium 46 



9. Larval Asymmetry 49 



10. The Mesodermal Somites 51 



11. TheNephridia 53 



12. The Larva at the Critical Stage . .......... 54 



IV. THE ADOLESCENT PERIOD . . 55 



1 



