560 Mr. A. H. Thayer on 
form in widely separated orders, plainly accompanying 
common environment and habits. The Salmon’s silver, 
grading upward into dusky, and downward to purest 
white, is identical with that of countless fish in many 
groups, and no one doubts that environment and habits 
are the cause. Among birds, Emberiza miliaria, Anthus 
pratensis, Alauda arvensis, and Alauda arborea are four 
species of three genera for all four of which one minutest 
colour-and-pattern-description would almost suffice; and 
the same colour-scheme and pattern with slight varia- 
tions is found on a great many other species throughout 
the world, both of Passeres and even Scolopacide and 
Galline, telling plainly of life on the ground amidst 
grasses. Among the Scolopacidxe, many females and young 
of the Anatide, and the Laridx, Nature betrays, in the 
main, great lack of variety in design, easily accounted for 
by the lack of variety in the aspect of the environment. 
In a broad survey of the animal kingdom we perceive that 
everywhere the degree of colour-and-pattern difference 
between different members of an order, family, or genus 
keeps pace with the degree of variation in their environ- 
ment’s aspect. 
Why may not the circumstances of a group of butterflies 
furnish them similar needs to wear a common livery, even 
if we cannot see the reason? Might they not tend also 
to have their flavour similarly affected by similar food ? 
The Spruce Grouse (Canachites canadensis) is saturated 
with spruce flavour, and the world is full of such cases. 
Even the amazing similarity between members of these 
groups is no proof they may not, for reasons which we 
have not discovered, profit each by exactly the same form 
of concealing-coloration. It should be borne in mind that 
it is not a flower that these mimics evidently represent, 
but a certain combination of the flower’s aspect with that 
of its surroundings. Hence there may be one best way 
to render this. Butterflies on wing are conspicuous, but 
are wonderfully protected by their jerky flight, which is 
completed by their wings being so large as necessarily 
to throw the body up and down at every movement. 
This latter advantage, attainable by no other conceivable 
means, may be a great factor in the whole matter. In 
flight they are doubtless practically safe, 7. ¢. too trouble- 
some a quarry to be seriously decimated. I send, for 
Professor Poulton to exhibit, photographs of a number 
