45 § 
The Progress of the 
[October, 
will be familiar with the curious case of the pigs in Virginia 
mentioned by Mr. Darwin. All white pigs, it appears, were 
destroyed by feeding upon a certain root which took no 
effeCt upon black pigs. This remarkable phenomenon is 
ascribed by Mr. Darwin to a constitutional peculiarity con- 
nected with the dark colour, the black animals enjoying a 
perfect immunity from the effects of a poison which was 
fatal to all of the white variety. Dr. Ogle, however, gives 
a different and more probable explanation. He remarks 
that we have no evidence that the black pigs partook of the 
root at all. He considers that it possessed an odour or a 
flavour offensive to their senses, while the white pigs — en- 
dowed with less acute and discriminating smell and taste — 
ate it and perished. This faCt is an admirable instance of 
the importance of acute senses to the preservation and 
multiplication of a species. Yet at the same time an 
advance in this respeCt can rarely be assumed to modify 
the structure of an animal or cause it to develope into a 
new species, even though acuteness or dulness of the senses 
may be respectively correlated with certain colours. 
With the acuteness of the senses and its progressive 
development is naturally connected the history of colour, 
odour, and flavour in the world. Have the faculties and 
their objects been evolved in mutual harmony ? Especially 
was colour existent before the colour-sense of animals had 
become able to recognise it — a process which, as we learn 
from the existence of colour-blindness, is even yet not 
complete. Are we to expeCt further advances as in the 
faculty, so in what it perceives ? 
Mr. Wallace considers that “ when the sense of sight was 
first developed in the animal kingdom, we can hardly doubt 
that what was perceived was light only, and its more or less 
complete withdrawal. As the sense became perfected, more 
delicate gradations of light and shade would be perceived. 
At what grade in animal development the new and more 
complex sense — which takes cognizance not merely of the 
quantity of light, but also of its quality — -first began to 
appear we have no means of determining.” It was a some- 
what prominent tenet of the old Natural History that the 
phenomena of colour, and indeed of ornamentation, in 
Nature, existed mainly in reference to man and with a view 
to his delectation. Mr. Wallace by no means agrees with 
many leading modern naturalists in the complete rejection 
of this assumption. He asks — “And even now, with all 
our recently acquired knowledge of this subject, who shall 
say that these Old-World views were not intrinsically and 
