496 THE ZOOLOGIST. 
to the gizzard; this swells out into a strong muscular throat or 
pharynx. On each side of the gullet are glands secreting lime. 
The gullet itself ends in a crop, which leads into a powerful 
gizzard: this, like the corresponding organ in a bird, contains 
stones for grinding the food. These stones in a full-sized worm 
are so large that nine or ten of them laid side by side will 
measure a full inch. The intestine passes straight from the 
gizzard to the end of the body. Worms have no lungs, breathing 
by their moist skin; hence they rapidly perish when exposed to 
dry air, though capable of prolonged life under water. Their 
senses are peculiar. They have no eyes, yet appear sensitive to 
light, which must pass through the transparent skin to reach the 
nerves. Thus they distinguish day and night, and avoid the 
dangers of exposure to their enemies, the birds, during the former 
period. Sound, unless accompanied by vibration of the ground, 
produces no effect on them, but they are sensitive of the slightest 
touch, even of a current of air. Their food is chiefly half-decayed 
leaves, but they are also carnivorous, and even prey upon the 
dead bodies of their own kind. The dead leaves they drag into 
their burrows, partly for food, and partly to close the openings. 
The leaves are seized by the lips, and then the anterior part of 
the body is formed into a kind of sucker. When leaves are not 
to be obtained for food, they swallow large quantities of mould, 
digesting the vegetable matter, and voiding the mineral portion in 
the form of worm-casts at the mouths of the burrows. 
In plugging up the mouths of their burrows, they evince a 
remarkable degree of intelligence. In order to test this, Mr. 
Darwin scattered a few hundred elongated triangles of paper over 
the ground, after removing all the fallen leaves he could see. 
These triangles, cut out of writing-paper, were rubbed with raw 
fat on both sides to prevent their becoming too limp when 
exposed at night to rain and dew. He found that, in the majority 
of cases, the worm on seizing a triangle selected the most 
pointed angle to draw into its burrow; in other words, it seized 
it in the position in which it could most easily be made to 
effect the object in view. In considering the question whether 
such action is intelligent or non-intelligent, Mr. Darwin adopts 
the argument that we can safely infer intelligence only when we 
see an individual profiting by its own individual experience; and 
he adds that if worms are able to judge either before or after 
