weakness or disease, and since the Grouse-disease is infectious, one such bird allowed at 
large may taint a whole covey. 
The substance of this reasoning is implied by Darwin himself in the concluding 
sentence of his chapter on the struggle for existence : ‘*‘ When we reflect on this struggle, 
we may console ourselves with the full belief that the war of nature is not incessant, that 
no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the 
happy survive and multiply.” 
YELLOW-THROATED VIREO. YELLOW-THROATED 
GREENLET. 
Vireo flavifrons. 
Above olive-green, brightest on the head and shading to blue-gray on 
the rump; sides of neck and of breast olive-green : throat and centre 
of breast yellow; belly white ; forehead yellow and a ring of yellow 
encircling the eye; wings brown with two white bands, and many of 
15t 
