say that Mr. Bates, after the attention he has bestowed upon this
question, is a zealous advocate of the hypothesis of the origin
of species by derivation from a common stock. After giving an
outline of the general distribution of Monkeys, he clearly argues
that unless the "common origin at least of the species of a
family be admitted, the problem of their distribution must remain
an inexplicable mystery." Mr. Bates evidently thoroughly
understands the nature of this interesting problem, and in
another passage, in which the very singular distribution of the
Butterflies of the genus Heliconius is enlarged upon, concludes
with the following significant remarks upon this important
subject:

"In the controversy which is being waged amongst Naturalists
since the publication of the Darwinian theory of the origin of
species, it has been rightly said that no proof at present
existed of the production of a physiological species, that is, a
form which will not interbreed with the one from which it was
derived, although given ample opportunities of doing so, and does
not exhibit signs of reverting to its parent form when placed
under the same conditions with it. Morphological species, that
is, forms which differ to an amount that would justify their
being considered good species, have been produced in plenty
through selection by man out of variations arising under
domestication or cultivation. The facts just given are therefore
of some scientific importance, for they tend to show that a
physiological species can be and is produced in nature out of the
varieties of a pre-existing closely allied one. This is not an
isolated case, for I observed in the course of my travels a
number of similar instances. But in very few has it happened that