Jeffries.] 240 [February 7, 



23. Fraise, Dr. C. Ueber Z'ahne bei Vbgeln. Wurzburg, 1880. 



24. Gotte, Dr. U. Beitrage zur Entwickelungsgeschichte des Darmkanals 



im Hiihnchen. Tubingen, 1867. 



25. Kossmann, R. A. Ueber die Talgdriisen der Vogel Zeitschr. f. 



Wissen. Zool. 21 Bd., ss. 568-599. 

 The few titles marked with an asterisk have of necessity been taken 

 second hand. 



EXPLANATION OF PLATES 4, 5, AND 6. 



Fig. 1 . Section of naked skin from the head of a gannet. (Sula bas- 

 sana.) Hartnack obj., 7 oc. 2. a, horn-layer; b, transitional cells; c, mucous 

 layer; d, pigment cells ; e, cutis vera. 



Fig. 2. Section of eptderm of 111 hours chick. Obj. 7 camera, a, epi- 

 trichial ; b, mucous layer. 



Fig. 3. Same of 134 hours chick. 



Fig. 4. Surface view of epitrichial layer of 14 days chick. 7 camera. 



Fig. 5. Section of epiderm of 17 days duckling. 7 camera. 



Fig. 6. Transverse section of feather papilla near tip, duck 20 .days, 

 7 camera, a, epitrichial ; b, loose horn cells, c, granular horn cells ; d, one 

 of the two primitive barbs ; e, pulp. 



Fig. 7. Transverse section of feather papilla low down, duck 18 days. 

 4 camera. Letters the same as before. 



Fig. 8. Longitudinal section of feather papilla of duck 20 days. 

 7 camera, a, epitrichial ; b, horn cells; c, row of forming barbuies ; d. 

 barbe, capillary of pulp full of blood globules. 



Fig. 9. Section of scutum, duck 17 days. 7-2. a, epitrichial; &, mucous 

 layer ; c, pigment. 



Fig. 10. Epitrichial-like coat from the pinfeather of a robin. (T. migra- 

 torius). 7 camera. 



Fig. 11. Longitudinal section of adjacent walls of feather papilla and 

 sack, 7-3. «, epitrichial-like coat; b, horn cells; c, transitional cells; d. 

 mucous layer of pocket ; b' c r and d' the same of pocket. 



Fig. 12. Section of pinfeather of robin. X20 . a, shaft; 6, horn case; 

 c, outer cell layer ; d, vane ; e, point of division of the two vanes ; f, pulp ; 

 g, pith of shaft. 



Fig. 13. Transverse sections of forming barb and barbuies of pinfeather. 

 7 camera. 



Fig. 14. Same of nearly complete barbs. 3 camera. 



Fig. 15. Longitudinal section of tarsus of 12 days chick, 9 im.-2. 

 a, epitrichial ; b, transitional cells ; c, mucous layer. 



Fig. 16. Same of 14 days chick. 7 camera, p, pigment. 



Fig. 17. Longitudinal section of scutum of 18 days chick. 7-3. a, epi- 

 trichial ; &, ill developed cells ; c, transitional cells ; d, mucous layer ; 

 e, mesoderm. 



