Departure for England 295 
mimetic forms has been most potent in moulding the form 
and coloration of species, and in some the two forces are seen 
to be opposed in their operation. Thus in some butterflies 
that mimic the Heliconide, the females only are mimetic, the 
males retaining the normal form and coloration of the group 
to which they belong. In such cases it appears as if the 
females have not been checked in gradually assuming the 
disguise they wear, and it is important that they should be 
protected, as they are more exposed to destruction while 
seeking for places to deposit their eggs; but that both sexes 
should not have inherited the change in form and colour 
when it would have been beneficial to both can only be ex- 
plained, I think, on the supposition that the females had a 
choice of mates and preferred those that retained the prim- 
ordial appearance of the group. This view is supported by 
the fact that many of the males of the mimetic Leptalides 
have the upper half of the lower wing of a pure white, whilst 
all the rest of the wings is barred and spotted with black, 
red, and yellow, like the species they mimic. The females 
have not this white patch, and the males usually conceal it by 
covering it with the upper wing, so that I cannot imagine its 
being of any other use to them excepting as an attraction in 
courtship, to exhibit to the females, and thus gratify a deep- 
seated preference for the normal colour of the order to which 
the Leptalides belong. 
I finally left the mines September 6th, 1872, on my way to 
England. I was accompanied through the forest by several 
of the mining officials. ‘Though glad to return to Europe, it 
was not without some feeling of regret that I rode for the 
last time through the forest where I had so often wandered 
during the years I had been at Santo Domingo. The woods 
had become as familiar to me as home scenes. No more 
should I see the white-headed ruby humming-bird come 
darting down the brook, chasing away the green-throat from 
its bathing-place; no more watch the flocks of many-coloured 
birds hunting the insects in the forests, or admire the wonder- 
ful instincts of the tropical ants. I listened with pleasure 
to the last hoarse cries of the mot-mots, and tried to im- 
press on my memory the curious forms of vegetation—the 
