1916] Chandler: Structure of Feathers 347 
c) Down 
The downy structure in Calopezus and Nothura is exactly the 
same as in typical gallinaceous birds, not only in the structure of 
the typical basal barbules of the distal vanule, which have detach- 
able rings of the same form, but also in the method and degree of 
simplification in other parts of the barbs. In Tinamus and Notho- 
cercus, on the other hand, the detachable rings are only slightly 
developed, but the more basal nodes are very much enlarged, while 
the more distal ones are in the form of tiny droplets, the type of 
barbule thus resembling that of the Columbae very closely (pl. 25, 
fig. 49f). Im all species the down barbules are very long, as in 
typical gallinaceous birds. 
ad) Relationships 
The structure of the down alone is sufficient proof that the 
tinamous are unquestionably far more closely allied to the Galli 
than to any other birds, since it is difficult to believe that the 
peculiar detachable rings at the nodes would be developed twice, by 
separate paths of evolution. The remarkable similarity of the down 
of some species to that of the Columbae can more readily be thought 
of as parallel evolution, since it is a type which recurs again in the 
Rhamphastidae, for instance, and is very easily derived from the 
gallinaceous type of structure. The occurrence of these two types 
of down in this single order, however, is suggestive of the fairly 
close relationship of the Colwmbae and Galli. 
The Crypturiformes show a remarkable number of specializations 
of feather structure which are absolutely pecuhar to them; in 
fact, it may safely be said that the barbs of tinamous have the 
most perfect and highly specialized interlocking mechanism found 
anywhere in birds. This fact alone is enough to show the error 
of grouping them with the Ratitae, or even anywhere near them. 
They must undoubtedly be looked upon as a highly modified offshoot 
from the Galliformes, if the feather structure be taken into account 
at all. 
e) Summary 
Crypturiformes are characterized as follows: 
(1) Plumules sparse, and found only between contour feathers. 
(2) Aftershaft present, often rudimentary, when well developed 
with long shaft and distinct vanes. 
