Zool. Soc._, 1865, p. 568). In the same
paper it is stated that the number of dorsal vertebrae in man is
normally twelve, very rarely thirteen. In the Chimpanzee there are
normally thirteen dorsal vertebrae, but occasionally there are fourteen
or only twelve.
_Variations in the Skull._
[Illustration: FIG. 14.--Variation of Skull of Wolf. 10 specimens.]
Among the nine adult male Orang-utans, collected by myself in Borneo,
the skulls differed remarkably in size and proportions. The orbits
varied in width and height, the cranial ridge was either single or
double, either much or little developed, and the zygomatic aperture
varied considerably in size. I noted particularly that these
variations bore no necessary relation to each other, so that a large
temporal muscle and zygomatic aperture might exist either with a large
or a small cranium; and thus was explained the curious difference
between the single-crested and the double-crested skulls, which had been
supposed to characterise distinct species. As an instance of the amount
of variation in the skulls of fully adult male orangs, I found the width
between the orbits externally to be only 4 inches in one specimen and
fully 5 inches in another.
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