Exact measurements of large series of comparable skulls of the mammalia
are not easily found, but from those available I have prepared three
diagrams (Figs. 14, 15, and 16), in order to exhibit the facts of
variation in this very important organ. The first shows the variation in
ten specimens of the common wolf (Canis lupus) from one district in
North America, and we see that it is not only large in amount, but that
each part exhibits a considerable independent variability.[23]
In Diagram 15 we have the variations of eight skulls of the Indian
Honey-bear (Ursus labiatus), as tabulated by the late Dr. J.E. Gray of
the British Museum. For such a small number of specimens the amount of
variation is very large--from one-eighth to one-fifth of the mean
size,--while there are an extraordinary number of instances of
independent variability. In Diagram 16 we have the length and width of
twelve skulls of adult males of the Indian wild boar (Sus cristatus),
also given by Dr. Gray, exhibiting in both sets of measurements a
variation of more than one-sixth, combined with a very considerable
amount of independent variability.
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