150 Dwicnut, Moult of Quazls and Grouse. heal 
during this period and others only one, while all of them are 
dormant during the long winters. The ‘generations’ of feathers 
are most frequent where the blood supply is richest. Problems 
of plumage solve themselves as soon as we can say when and 
where each feather grows, and a comprehension of the idea of 
sequence is the key to the whole matter. 
Before taking up the series of plumages and moults in their 
natural order of development in the Ptarmigans, I wish to call 
attention to Plate IV which shows the four constant types of 
feathers found upon Lagopus /agopus. It is the mingling of the 
four that has proved a stumbling block to many observers. Fig. 
1 represents one type, the juvenal plumage; Figs. 2, 3, and 10 a 
second type, the preliminary winter plumage; Figs. 4 and 11 a 
third type, the supplementary winter plumage; and Figs. 5-9 a 
fourth type, the nuptial plumage. That feathers of all of these 
types grow at definite times is amply shown by many of the series 
of birds examined and is illustrated by Figs. 9, 10 and 11 which 
show new feathers still clasped by their sheaths; but it must be 
remembered, there is some tendency for one type to run into 
another. My object is to indicate when and where these types 
grow and how they are modified in color and pattern by age, sex, 
individuals, and particularly by position. If observers would pay 
attention to a few of these matters first we would hear very little 
afterwards about color change without moult. The parti-colored 
feathers are principally on the line of demarkation between light 
and dark areas, and the same style of feathers will always be 
found upon corresponding areas of birds taken at the same stage 
of development. The feathers of the second type, for instance, 
always show an amount of white basally which varies with the 
position they occupy in the feather tracts. The white, too, is 
most extensive upon the webs nearest white areas, just as it is in 
Dendragapus, or any other species with contrasting colors. This 
may be seen by examination of the feathers of the mesial borders 
of the sternal bands of the ventral feather tract where dark parti- 
colored feathers largely tipped or variegated with white are regu- 
larly produced at the postnatal, postnuptial and prenuptial 
moults. The triangular wedge of ventral feather tract extending 
between the sternal bands produces only white feathers at the 
