1916] Chandler: Structure of Feathers 365 



Cuculidae in the structure of their feathers, although, as will be 

 shown later, they have a peculiar pigmentation. 



The Psittaci differ from the Cuculi to a very slight degree. The 

 barbules of the remiges, as exemplified by Cacatua galerita (pi. 30, 

 figs, l^a-d), differ in no important details except the character 

 of the proximal barbules of the distal part of the outer vane, 

 where, instead of the pennulum being long with well-developed 

 hooked cilia as in Coccyzus (pi. 30, fig. 72(Z), the base is shortened, 

 the pennulum also short, and the ventral teeth somewhat increased 

 in number, separated, and in the form of short, more or less tri- 

 angular barbicels (pi. 30, fig. 74(i). 



Melopsittacus differs in having distal barbules of the outer vane 

 (pi. 30, fig, 75a) with rather stout bases and short pennula with 

 crowded cells, the booklets being long and closely approximated to 

 one another and the ventral cilia also rather crowded. The proximal 

 barbules undergo the same sort of modification on the outer part of 

 the barb as in Cacatua (pi. 30, fig. 75&). 



The body feathers of the Psittaci resemble those of the Cuculi, 

 but differ in that the barbicels are all less highly developed (pi. 30, 

 figs. 76a, 77a, 776). In breast feathers, frequently, practically 

 all the barbicels are rudimentary or absent, except two or three 

 rather conspicuous booklets on the distal barbules (pi. 30, figs. 77a, 

 77&). 



c) Doivn 



The down in Coccyzus, Cuculus, and Eudynamis resembles that 

 of the typical Columbidae rather closely, but can readily be dis- 

 tinguished. The barbules are long (2 mm. more or less) and very 

 slender, and the nodes are in the form of round droplets some- 

 what resembling the viscid droplets on a spider's thread. Those 

 near the base are large, while more distally they are very minute, 

 but still maintain their globular form. In pigmented barbules 

 the pigment is localized in a spot just back of the globular node. 

 The internodes are exceedingly long and slender, in Eudynamis 

 honorata sometimes 0.1 mm. long and less than 0.002 mm. in dia- 

 meter. In Geococcyx the globular nodes are not in evidence, the 

 cells being merely gradually enlarged, and pigmented on their distal 

 half. 



The down of the Psittaci very closely resembles that of the typical 

 cuckoos, having more or less globular nodes which are rather large 



