Raymond Pearl and Maud Dewitt Pearl 
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(2) An anterior region (Diagram A, h) having its free border smooth or 
very slightly and irregularly serrated, typically never deeply and regularly serrated. 
(8) A middle, serrated region (Diagram A, c). This is the region of the 
deep and characteristic serrations on the free border of the comb. 
(4) A posterior region or blade (Diagram A, d) typically having its dorsal, 
posterior and ventral borders free, and lying wholly behind the posterior end of the 
base (a) of the comb. 
A study of the figures in Plates I. to III. makes it evident that variation occurs 
in respect to each of these comb regions. A summary catalogue of these variations 
is presented because of its possible usefulness in classifying single comb variations 
in breeding work. The several regions enumerated are considered in order. 
The basal region (a) may be present or absent. When present it varies in height 
above skull, showing all gradations between entire absence and a height of several 
millimetres. In some cases (for example, Figs. 16, 17 and 19) the vane is directly 
attached to the skull without any intervening, morphologically distinct base. In 
the living bird this condition most obviously manifests itself by the ventral edge 
of the blade lying close down to the head. This condition was observed in 6 out 
of the 81 combs measured. 
The anterior portion (b) may vary in regard to the following particulars * : 
(1) Relative extent. (Compare Figs. 2, 22, 30, 36, 40, 50, 65, 78 and 93.) 
This region reaches back over considerably more than half the length of the comb 
in some cases, and only a short distance in others. 
(2) Character of serration varies all the way from a perfectly smooth free 
margin (Figs. 2, 29, 43 and 63) through a condition of fine and regular serration 
(Figs. 8, 9, 62, 84 and 86) to a condition of coarse and irregular points in this 
region of the comb (Fig. 75). 
(3) General shape varies from the condition in which the free border is 
generally convex (Figs. 29, 30, 54, 63, 69, 70, 93, 94) through the condition where 
the border is approximately straight (Figs. 7, 12, 26, 28) to the concave or ex- 
cavated border (Figs. 23, 31 and 33). 
The middle or serrated portion (c) may vary in respect to : 
(1) The depth of the serrations. The serrations may be broad and deep 
(Figs. 13, 19, 24, 92 and 94), or broad and shallow (Figs. 10 and 89), or narrow 
and deep (Figs. 11, 26, 75, 88 and 96), or, finally, they may be shallow and narrow 
(that is set close together. Figs. 27 and 51). All degrees of gradation between 
these classes are represented among the combs. 
* It is to be understood that the references to figures given in parentheses in this section are intended 
merely as illustrations, and not as complete, statistical inventories of all the combs falling within each 
of the several categories. The attempt is made simply to refer to several clear illustrations of each 
class. 
