Origin of Species Variorum

→ two-thirds 1860 1861 1866 1869 1872

two thirds of 1859

→ OMIT 1860 1861 1866 1869 1872

the trees now growing on the 1859

→ which must formerly have been cleared of trees, now display 1860 1861 1866 1869 1872

display 1859

whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare, or wholly disappear. The number of humble-bees in any district depends in a great

measure

degree

on the number of field-mice, which destroy their combs and nests; and

Col.

Mr. H.

Newman, who has long attended to the habits of humble-bees, believes that "more than →two-thirds

them

of them

are thus destroyed all over England." Now the number of mice is largely dependent, as every one knows, on the number of cats; and

Col. Newman

Col.Newman

Mr. Newman

says, "Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the

numbe

number

r of

cats that destroy the mice." Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!

In the case of every species, many different checks, acting at different periods of life, and during different seasons or years, probably come into play; some one check or some few being generally the most

potent;

potent,

but all

concurring

will concur

concur

in determining the average number or even the existence of the species. In some cases it can be shown that widely-different checks act on the same species in different districts. When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this! Every one has heard that when an American forest is cut down, a very different vegetation springs up; but it has been observed that →OMIT ancient Indian

mounds,

ruins

in the Southern United States, →which must formerly have been cleared of trees, now display the same beautiful diversity and proportion of kinds as in the surrounding virgin

forest.

forests.