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ROYAL HORTICULTURAL SOCIETY. 
would produce the hybrids. That granted, I would remind the 
reader of what Mr. Bates has obviously overlooked, that we are 
dealing with a phenomenon probably of a very ancient date, and 
that one side of the parental stock may have disappeared in the 
course of time. I have elsewhere suggested, in regard to hybri- 
dization as a possible originator of species, that it must be a neces- 
sary accession to such an event that the hybrids should have 
opportunity of isolation, such as might be obtained by thinly 
peopled districts where they might settle, spread, and establish 
themselves. Now, certainly, the Valley of the Amazons, the 
Malayan Archipelago, and many parts of the South of Africa 
(lands whence these mimetic analogies come) have at different 
periods all been at one time unoccupied land ; for all of them 
have been raised from the bottom of the sea, and been peopled by 
the influx of the inhabitants of neighbouring lands. No one 
knows better than Mr. Bates that at one time Brazil was uncon- 
nected with New Granada or the Andes. The Danaids were then 
inhabitants of it, but not inhabitants of the countries about it ; 
while the Pieridse, or cabbage whites, were what I have elsewhere 
denominated a microtypal tribe from more temperate climes, and 
were present in the Andes and the mountain countries, as 
Columbia, connected with them. In the natural course of things, 
therefore, when the Valley of the Amazons was changed from the 
bottom of a sea to dry land, the Danaids would spread into it 
from Brazil, and the Pieridae from the north and west, and meet- 
ing in an open, as yet, unpeopled country, hybridization might 
take place under one of the few circumstances where I have 
thought it possible that it could retain its place and establish 
its products as species. The objection that frightened off* Mr. 
Bates is, in reality, no objection at all to the hypothesis of the 
mimicry being due to hybridization, that we are not always, or 
even that we should not at all be able to identify the probable 
parents of the mimickers as inhabitants of the same country as 
their supposed descendants. One of the parents we know to 
be present (the so-called mimicked), but there are excellent 
reasons why the other parent should not be present. It is of 
a northern type, suited for our temperate regions, but not adapted 
to the tropics except at a higher elevation and a cooler tempera- 
ture than the damp, hot valley of the Amazons. Although, 
therefore, it might descend into that region, it is not only a 
natural but almost a necessary inference that it would not find 
