in his work on the "Geographical
Distribution of Mammals," p. 53, and represented in the frontispiece by
figures copied from Gould's "Mammals of Australia;" but instances enough
for the present purpose have been already quoted.

Additional reasons for believing that similarity of structure is produced
by other causes than merely by "Natural Selection" are furnished by certain
facts of zoological geography, and by a similarity in the mode of variation
being sometimes extended to several species of a genus, or even to widely
different groups; while the restriction and the limitation of such
similarity are often not less remarkable. Thus Mr. Wallace says,[62] as to
local influence: "Larger or smaller districts, or even single islands, give
a special character to the majority of their Papilionidae. For instance:--1.
The species of the Indian region (Sumatra, Java, and Borneo) are almost
invariably smaller than the allied species inhabiting Celebes and the
Moluccas. 2. The species of New Guinea and Australia are also, though in a
less degree, smaller than the nearest species or varieties of the Moluccas.
3. In the Moluccas themselves the species of Amboyna are the largest. 4.
The species of Celebes equal or even surpass in size those of Amboyna. {84}
5. The species and varieties of Celebes possess a striking character in the
form of the anterior wings, different from that of the allied species and
varieties of all the surrounding islands. 6. Tailed species in India or the
Indian region become tailless as they spread eastward through the
Archipelago. 7. In Amboyna and Ceram the females of several species are
dull-coloured, while in the adjacent islands they are more brilliant."
Again:[63] "In Amboyna and Ceram the female of the large and handsome
_Ornithoptera Helena_ has the large patch on the hind wings constantly of a
pale dull ochre or buff colour; while in the scarcely distinguishable
varieties from the adjacent islands, of Bouru and New Guinea, it is of a
golden yellow, hardly inferior in brilliancy to its colour in the male sex.
The female of _Ornithoptera Priamus_ (inhabiting Amboyna and Ceram
exclusively) is of a pale dusky brown tint, while in all the allied species
the same sex is nearly black, with contracted white markings. As a third
example, the female of _Papilio Ulysses_ has the blue colour obscured by
dull and dusky tints, while in the closely allied species from the
surrounding islands, the females are of alm