Raymond Pearl and Maud Dewitt Pearl 
431 
(4) The angle made luith the base of the comb. The blade may be set 
on the comb in such a way that its chief axis is approximately in line with 
the chief axis of the comb (Figs. 4, 9, 10, 2G, 42, 49, 50, 67 and 94), or it may 
be tilted up so that its axis forms different angles with the rest of the comb 
(Figs. 3, 8, 11, 15, 20, 30, 32, 02, 64, 77, 80 and 87). It is even possible that 
the blade may be tilted downward with reference to the rest of the comb as 
is shown, for example, in Fig. 35. 
6. The comb as a whole may vary in form in certain other respects beyond 
those enumerated. Some of these variations are not shown in the series of figures 
here presented. Among such variations are to be included lopping of the comb, 
such as is a normal breed characteristic of Leghorn hens, and of other breeds 
having a very large single comb. The comb may also be wrinkled or puckered. 
This condition is brought about when the area of the vane of the comb is too 
great for the base, and consequently puckering of the free border of the vane 
occurs. An example of this condition is indicated by the dotted line in Fig. 38. 
Another variation of the single comb is that in which side sprigs or points 
occur. Examples of this variation are shown in Figs. 73 and 76. These side 
sprigs occur with tolerable frequency among single comb breeds of fowls. They 
usually appear more often in the males than in the females. The fancier must 
constantly be on his guard to keep this form of comb from appearing among his 
exhibition birds. The occurrence of this comb variant is of particular interest 
from the theoretical side, because there is strong reason to regard it as an in- 
cipient transitional or intermediate form between the pure single and the pure 
pea types of comb. The pea comb diffei-s from the single comb in that in addition 
to a central ridge corresponding to the vane of the single comb, it has two lateral 
serrated ridges of comb substance. Neither the central nor the lateral ridges of 
the pea comb are nearly as high as is the vane of the single comb. The low, 
compact form of the pea comb is one of the characteristic features which dis- 
tinguish it from the single comb. Side sprigs occurring on the single comb appear 
in just the place where the lateral ridges of the pea comb lie in the corresponding 
region of the comb. Davenport iloc. cit. p. 66) says of them : " Now such side 
sprigs are morphologically equivalent to the lateral ridges of the pea comb." When 
the side sprigs are present, they are usually found near the posterior end of the 
comb. It is a well-known fact to breeders who handle pea comb birds that 
when the pea comb is partially defective it is usually at the posterior end alone 
that the three ridges (central and two laterals) are found. 
That intermediate forms between the pea comb and the single comb occur has 
been knoAvn for some time. In 1902 Bateson*, in describing the results of crossing 
White Leghorns (single comb) and Indian Games (pea comb) says : " In the cross- 
bred the comb is almost always either a true single comb, differing from the White 
Leghorn in diminution of size ; or an intermediate pea. Of the latter there are 
* Report to the Evolution Committee of the Koyal Society. Report I, 1902, p. 94. 
