occurred most frequently on the neck, ears, face, thighs, hind legs, about
the root of the tail, and occasionally on the tail itself. In only one
instance were the ears white, and that in the case of one of the offspring
of a male which was distinguished from most of his fellows by the
possession of one white ear. I have had a few individuals whose markings
were white and gray instead of white and black.

The method by which I was able to keep an accurate record of each of my
dancers for purposes of identification and reference is illustrated in
Figure 1. As this method has proved very convenient and satisfactory, I
may briefly describe it. With a rubber stamp[1] a rough outline of a
mouse, like that of Figure 1 A, was made in my record book. On this
outline I then indicated the black markings of the individual to be
described. Beside this drawing of the animal I recorded its number,
sex,[2] date of birth, parentage, and history. B, C, and D of Figure 1
represent typical color patterns. D indicates the markings of an
individual whose ears were almost entirely white. The pattern varies so
much from individual to individual that I have had no trouble whatever in
identifying my mice by means of such records as these.

[Footnote 1: For the use of the plate from which this stamp was made, I am
indebted to Professor W.E. Castle, who in turn makes acknowledgment to
Doctor G.M. Allen for the original drawing.]

[Footnote 2: I have found it convenient to use the even numbers for the
males and the odd numbers for the females. Throughout this book this usage
is followed. Wherever the sex of an individual is not specially given, the
reader therefore may infer that it is a male if the number is even; a
female if the number is odd.]