LIST OF WOODCUTS. 



FIG. PACK 



1. Diagram of the Unimpregnated Ovum 3 



2. Diagrams of the Segmentation of the Ovum 4 



3. Diagram of a Segmented Meroblastic Ovum 5 



4. Blastosphere 5 



5. Gastrula 6 



6. Early Stage in the Differentiation of the Embryo 7 



7. A and B. Diagrammatic Transverse Sections through a Developing Verte- 



brate Embryo 8 



8. Diagrammatic Transverse Section through the Body of an Adult Vertebrate 9 



9. A, B, and C. Diagrams illustrating the Formation of the Amnion, Allantois, 



and Yolk-Sac. A and B, in Longitudinal Section ; C, in Transverse 



Section 11 



10. Diagrammatic Transverse Section illustrating the Structure of the Skin in 



Fishes ] 7 



HA. Skin of Larva of Salamander (Salamandra niaculosa) 19 



HB. Section through the Skin of Adult Salamander (S. maculosa) 19 



12. Six Stages in the Development of the Feather. (Mainly after Th. Studer. ) 21 



13. Six Stages in the Development of Hair 23 



14. Longitudinal Section through a Hair. (Diagrammatic.) 25 



15. Section through the Human Skin 26 



16. A, True (Secondary) Teat ; and B, Pseudo- (Primary) Teat 27 



17. a, Dermal Armature of Hypostoma commune (a Siluroid) ; b, Denticles from 



the Skin of the Abdomen of Cdlliehthys ; c, Plates from the Tail-fin of 



Hypostoma. (After O. Hertwig.) 30 



18. Dermal Denticles of Protoptcrus 31 



19. Dermal Armature of Calliehthys 31 



20. Transverse Section of the Vertebral Column of Ammoccetcs 34 



21. Portion of the Vertebral Column of Spatularia. (Side view. ) 35 



22. Transverse Section of the Vertebral Column of Acipenser ruthenus (in the 



anterior part of the body) 35 



23. Portion of the Vertebral Column of Protopterus. (Side view.) 35 



24. Portion of the Vertebral Column of Polyptrrus .... 36 



