... Darwin ... became the official naturalist on the five-year voyage of the "" (1831–1836) ... ... He also read the essay in which Malthus told of t… - Ann Haven Morgan

... The two problems which face every organism are those of maintaining its own life and continuing its race. Its youth is devoted entirely to satisfying its individual needs for food and safety; its adult life is devoted to the race, but the necessities of the individual are still satisfied though they may be secured in an entirely different way. The immature life of is aquatic, and to it all adjustments concerned with food or safety are exclusively confined. The mature or adult life is aerial. It is solely devoted to reproduction. There is no provision for food or for other means of lengthening its life. It gives an opportunity for studying ways of getting a living which have been completely isolated from ways of reproducing.

No one who has lived by clear waters can have failed to see something of their wonderful life: minnows on the shoals; dragging their cumbersome portable houses over the brook bed; the young of mayflies clinging to the stones in the riffle; or the adult mayflies in their dancing nuptial flight in the air above the stream; and what could be more interesting?

The s () of s repeat the essentials of kidney form and function, tubules closely associated with blood and body fluid, each one a guardian of the content of the blood. There are two kidneys in nearly every segment of the earthworm ...