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Mr. Beddard remarks that all, or nearly all, the above variations are
found _normally_ in other genera and species.
When we consider the enormous number of earthworms and the comparatively
very small number of individuals examined, we may be sure, not only that
such variations as these occur with considerable frequency, but also
that still more extraordinary deviations from the normal structure may
often exist.
The next example is taken from Mr. Darwin's unpublished MSS.

"In some species of Shrews (Sorex) and in some field-mice
(Arvicola), the Rev. L. Jenyns (_Ann. Nat. Hist._, vol. vii. pp.
267, 272) found the proportional length of the intestinal canal
to vary considerably. He found the same variability in the
number of the caudal vertebrae. In three specimens of an
Arvicola he found the gall-bladder having a very different
degree of development, and there is reason to believe it is
sometimes absent. Professor Owen has shown that this is the case
with the gall-bladder of the giraffe."

Dr.


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