Chap. II. On the habits of worms 17

Nightcrawler

A diversion upon the formation of vegetable mould

Snake, but the animal is an earthworm, and the board a vertical section of garden soil twenty inches in depth. It feeds upon fallen leaves, which gather near the surface; it loosens every inch of earth it passes through; and it has no eyes, so that it must remember the burrow behind it. The mould continues at either hand. Above lies the open air, and below, the subsoil ends.

To begin.

Steer with the arrow keys, with W A S D, or with a finger drawn across the plate. Leaves gather near the surface: that is where the animal must go, and where the open air waits.

Fig. 1.—Vertical section of a garden soil, twenty inches in depth, showing the burrow of a full-grown Lumbricus terrestris, with its castings, fallen leaves, embedded stones, and a growth of fungal hyphæ. Drawn to the scale at the left.

Table I.—Observations

Leaves consumed	Segments	Depth of head	Best recorded
0	6	10in.	0

Directions.—The arrow keys or W A S D steer the animal; the space-bar suspends the observation; R begins it afresh. Upon a touch-screen, draw the finger across the plate.

^* After Darwin, The Formation of Vegetable Mould through the Action of Worms (London: John Murray, 1881), wherein the worms of an English field are reckoned to pass between ten and eighteen tons of earth to the acre through their bodies in the course of a single year. The castings dropped behind the animal here are that same labour, in little; and the pale swollen band a fifth of the way down its body is the clitellum, by which the cocoon is secreted, and the only sure landmark on a worm.