STUDIES OF THE MACROCHTRES. 



367 



On the throat of Swifts and Swallows the feathering covers 

 the entire area, while in Humming-birds the median naked space 

 of the neck is continued almost up to the base of the inferior 

 mandible. 



Again, Nitzsch noticed the naked " nape-space [see his figure] 

 beneath the long cornua of the hyoid bone," but " could not deter- 

 mine with precision " whether or no it was a constant character 

 for the pterylography in the Trochili. My investigations con- 

 vince me that it is a constant character in them, and, further, 

 that it is neve7^ present in the Swifts nor Swallows. If any one will 

 take the trouble to pluck a Humming-bird and note, in the 

 natural position of its head, that the back of the head comes 

 very close to the body, he will see at once how this naked space 

 has come to be present there. 



The arrangement of the pterylae upon the ventral aspects of 

 all of these birds is more or less alike, being apparent modifica- 

 tions of some Passerine type ; but not so with the spaces upon 

 the dorsal aspects, for here we find that the true diff'erences 

 among them come in (compare Nitzsch's figures). And we must 

 remember that Nitzsch, in speaking of the pterylography of the 

 Macrochires, was forced to admit that : — " In this family I place 

 the two genera Oypselus and Trocliilus, which, iudeed, ])resent 

 but little external similarity, but are very nearly allied in the 

 structure of their wings" (p. 86). To the near alliance on 

 account of the latter character we will revert later on. 



In the first part of this memoir I have attempted to point out 

 such diff'erences as exist between the pterylography of a Swift 

 and a Swallow, so it will not be necessary to enter so fully upon 

 the details again here. Be it borne in mind, however, that, 

 upon this dorsal aspect of the two, in both the humeral tract 

 crosses obliquely at a point opposite the middle of the humerus 

 of the arm ; in Trochilus, on the otlier hand, it is over the 

 head of the humerus. Swifts and Swallows both possess a femoral 

 tract ; whereas it is absent as a rule (and, for all that I know 

 to the contrary, always) in the Humming-birds — certainly so in 

 Trochilus. 



In Swifts the " spinal tract " connects the capital area behind 

 with the oil-gland, but just opposite the shoulder-joints bifur- 

 cates ; the bifurcations are as wide as the original tract, and 

 after passing the middle of the back they converge again, and 

 unite at a point over the anterior end of the sacrum. Thus we 



