290 CHAPTERS ON THE NATURAL HISTORY 



We have, then, the following feather tracts to study and com- 

 pare in birds with the view of assisting us in our classification of 

 this group of vertebrates, viz. : 



1. The spinal tract (Pteryla spinalis). 



2. The humeral tract (Pteryla humeralis). 



o. The femoral or lumbar tract (Pteryla femoralis sen lum- 

 balis) . 



4. The ventral tract (Pteryla gastrcei). 



5. The lateral neck tract (Pteryla colli lateralis). 



6. The head tract (Pteryla capitis). 



7. The wing tract (Pteryla alar is). 



8. The crural tract (Pteryla cruralis). 



9. The caudal tract (Pteryla caudalis). 



10. The postventral tract (Pteryla postventralis). 



There will, too, of course, be some anomalies to be on the look- 

 out for, as we see in the " internal humeral tract " and such 

 others like it. 



This chapter will not have been contributed in vain if it but 

 prove to be the means of inciting even one careful observer to 

 enter upon this very fruitful field of research. 



As for myself, I was never so fully impressed with the value 

 of pterylography as an aid to correct taxonomy in birds as I was 

 when I came to investigate this character and compare it in the 

 swifts and humming birds, forms by many supposed to be re- 

 lated to each other closely enough at least to place them in the 

 same order. I found the pterylosis in a swift very different from 

 the pterylosis in a humming bird, a fact which further supports a 

 former suggestion of mine, elsewhere published, to the effect 

 that these birds be placed in entirely different groups. 



