v COLOURS OF ANIMALS 389 
and the West Indies, and, among butterflies, in the smaller 
Moluccas, the Andamans, and Madagascar, we cannot avoid 
the conclusion that in these insular localities some general 
cause is at work. 
There are other cases, however, in which local influences 
seem to favour the production or preservation of intense 
crimson or a very dark coloration. Thus in the Moluccas 
and New Guinea alone we have bright red parrots belonging 
to two distinct families,| and which therefore most probably 
have been independently produced or preserved by some 
common cause. Here, too, and in Australia we have black 
parrots and pigeons ;? and it is a most curious and suggestive 
fact that in another insular sub-region—that of Madagascar 
and the Mascarene islands—these same colours reappear in 
the same two groups.3 
Sense-perception influenced by Colour of the Integuments 
Some very curious physiological facts bearing upon the 
presence or absence of white colours in the higher animals 
have lately been adduced by Dr. Ogle.* It has been found 
that a coloured or dark pigment in the olfactory region of 
the nostrils is essential to perfect smell, and this pigment is 
rarely deficient except when the whole animal is pure white. 
In these cases the creature is almost without smell or taste. 
This, Dr. Ogle believes, explains the curious case of the pigs 
in Virginia adduced by Mr. Darwin, white pigs being killed 
by a poisonous root which does not affect black pigs. Mr. 
Darwin imputed this to a constitutional difference accompany- 
ing the dark colour, which rendered what was poisonous to 
the white-coloured animals quite innocuous to the black. Dr. 
Ogle, however, observes that there is no proof that the black 
pigs eat the root, and he believes the more probable explana- 
tion to be that it is distasteful to them ; while the white pigs, 
being deficient in smell and taste, eat it and are killed. 
Analogous facts occur in several distinct families. White 
sheep are killed in the Tarentino by eating Hypericum cris- 
1 Lorius, Eos (Trichoglosside), Eclectus (Paleornithide), 
2 Microglossus, Calyptorhynchus, Turacena, 
3 Coracopsis, Alectranas. 
4 Medico-Chirurgical Transactions, vol. liii. (1870). 
