[28v]

10

lers. No explanation whatsoever is offered, as it seems to me, of the innumerable cases of exquisite and wonderful co-adaptation of organic beings one to another;— for instance in the often quoted case of the woodpecker, in which the feet and tail are formed to climb trees, the beak like a wedge to peck into the bark, and the wonderful tongue to secure the hidden insects;— or again with the misseltoe adapted to grow on certain trees and rob their sap, with their berries adapted to be carried by certain birds, and with their unibisexual flowers, absolutely requiring certain insects to transport their pollen. I do not believe a single animal exists without having manifest correlations to other organic beings. How are these facts to be explained? It seems futile to attribute quite impossible to explain them by the effects of changed external conditions, as of greater or less heat and light or of moisture and other such contingencies. To state that after many generations some plant gave birth to the misseltoe, with its threefold relation, appears to me to throw no more light on the problem, than to state simply that the misseltoe was

[28]

Leith Hill square yard

[calculations, not transcribed, for "The second square was marked on unenclosed common land, at a height of about 700 ft. above the sea, at some little distance from Leith Hill Tower. … The collected castings, after being well dried, weighed 7·453 pounds; and this would give, for an acre of the same kind of land, 16·1 tons of annually ejected dry earth." Earthworms, pp. 167-8.]