THE GENESIS OF FAULT-BARS IN FEATHERS AND 



THE CAUSE OF ALTERNATION OF LIGHT 



AND DARK FUNDAMENTAL BARS. 



OSCAR RIDDLE. 



With 4 Plates and 5 Figures in the Text. 



Contents. 



PAGE. 



1. Introduction 328 



2. The Morphology of Fault-bars '. 329 



(«) The Adult Feather 331 



(i) The Feather- germ ! 334 



3. The Extent and Distribution of Fault-bars 335 



(a) In the Bird Groups 336 



(i>) In the Various Plumages and Pterylse 336 



(c) In an Individual Feather 337 



4. The Experimental Production of Fault-bars 338 



(a) Reduced Feeding * 338 



(6) The Feeding of Sudan III 339 



(c) Effect of Mechanically Crumpling the Feather-germs 340 



(d) General 340 



(<f) The Production of Fault-bars with Amyl Nitrite 341 



5. The Homologies of Fault-bars , 344 



6. Feather Growth 345 



(a) The Region of Feather Growth 345 



(6) The Rate of Feather Growth 346 



(c) The Effect of Starvation on the Rate of Growth 346 



7. The Nutrition of the Feather 348 



(a) General on Feather Nutrition 348 



(i>) Structural Relations Between the Feather Elements and the Blood... 349 



8. Blood Pressure Rhythms in Birds 350 



9. Temperature Rhythms in Birds 352 



10. Relations of Pigment to Fault-bars and Nutrition 354 



11. Meaning and Cause of Fault-bars and Fundamental Bars 356 



12. Discussion 357 



13. Summary 361 



Introduction. 



During recent years several attempts have been made to find 

 a basis, structural or physiological, for the color patterns of vari- 

 ous animals. Among the most notable and successful of these 



328 



