'9^8.] Structure of the Feather. 245 



two-tliirds of the illustration shows the tegmen 'covering; 

 the space between the barbs. The barbs in the upper 

 one-third have open spaces between them with background 

 of barbules, 



Plate V. fig-. 2 is a portion of a barb from a Goosander 

 primary, magnified 55 times. This view shows the barb 

 from the side, and it will be seen that the tegmen entirely 

 covers the barbules on the left. Towards the right the tip 

 of the tegmen has become detached from the barb, which is 

 not usual. 



The tegmen appears in two forms, (1) a flat cover, (2) a 

 curved cover. There does not appear, however, to be any 

 particular system about the construction, for while the 

 Buzzai-d, Blackcock, Grey Partridge, Grouse, and Duck 

 have a flat tegmen, the Turkey, Pheasant, Capercaillie, 

 Goosander, Gull, and Owl have a curved tegmen. 



Plate VI. fig. 1 is the sectional surface of seven barbs 

 (in their original position) of a Turkey's primary, magnified 

 22 times. Here the impossibility of securing good definition 

 over the whole had to be met with an average focus. The 

 distal and proximal barbules are seen interlacing above and 

 from them depend the seven barbs, each barb terminating 

 in the curved form of tegmen which should close the space 

 between the barbs, but in arranging the subject it was 

 difficult to avoid disturbance. 



Plate VI. fig. 2. The above explanation applies to this 

 illustration, which represents a Pink-footed Goose's primary. 

 The barbules extend along the upper surface and the tegmen 

 appears as a flat cover on the lower side. In the original 

 position the construction Avas that of a series of tubes, but 

 in order to show the tegmen the barbs had to be slightly 

 separated. 



Plate VI. fig. 3 is a section similar to the above from a 

 Heron's primary. The section was cut outside the semi- 

 tegmenous area. This photograph was made to show an 

 instance of "no tegmen." The barbules are seen above 

 and the vertical pointed barbs below, shoAving the absence 

 of tegmen at the tips. 



