1886. ] CUBITAL COVERTS OF BIRDS. 201 
Gypagus, I have been so much impressed with the uniform style 
of wing-coverts prevailing amongst this group, that it seems to me 
difficult to believe that their genetic relationship amongst them- 
selves is more remote than Forbes regarded it. I cannot, after many 
years’ observation of the facts referred to in this paper, help re- 
garding this similarity of style of wing-coverts in birds so different, 
both in outward form and in their mode of life, as presenting us 
Fig. 34. 
Sarcorhamphus. 
with a certain amount of evidence of the transmitted survival, in an 
unmodified form, of a mode of imbrication of epidermic structures 
that at some remote period in the genetic history of the common 
Sauropsidan ancestors of these birds played some really important 
part in the economy of the wearer. During the differentiation of 
such parts of the creature’s organization as were directly affected by 
the struggle for existence, other parts, not so affected, either 
changed at a slower rate, or else were transmitted from generation to 
generation hardly modified at all. Habit, or mode of life, as birds 
now live, can at the most have played but a minor part in bringing 
about these diversities of style. We have but to compare the 
Swallows with the Swifts, the Sun-birds with the Humming-birds, 
and many other parallel cases, and we at once perceive that mode 
of life has had little or nothing to do with the origin of the features 
in question. The real cause lies deeper than that, and dates back 
far into the remote history of the Sauropsida. 
Reverting to the normal Ciconiine style of coverts, we find Platalea, 
with Jdis and its allied genera, differing but little from each other 
and from Ciconia. 
Tantalus, in this respect, stands nearer to the Limicole. 
The Cranes, again (fig. 35, p. 202), present another variation little 
removed from the central Pluvialine type. 
Somewhere near to the Cranes and the Storks, but connected in 
some way with the Gallinaceous style of coverts, stands the wing of 
the Secretary Bird (fig. 36, p. 202); it is quite unlike the true 
Accipitrine type. 
Proc. Zoou. Soc.—1886, No. XIV. 14 
