That all animals which feed on various substances possess the sense of taste, is a wise presumption. This is certainly the case with worms. Cabbage leaves are much liked by worms, and it would seem that they are able to distinguish between the different varieties, but this may perhaps be owing to differences in their texture. When leaves of the cabbage, horse-radish and onion were given together, they manifestly preferred the last to the others. Celery is preferred to the leaves of the cabbage, lime-tree, ampelopsis and parsnip, and the leaves of the wild cherry and carrots, especially the latter, to all the others. That the worms have a preference for one taste over another, is still further shown from what follows. Pieces of the leaves of cabbage, turnip, horse-radish and onion have been fed to the worms, mingled with the leaves of an Artemisia and of the culinary sage, thyme and mint, differing in no material degree in texture from the foregoing four, yet quite as strong in taste, but the latter were quite neglected excepting those of the mint, which were slightly nibbled, but the others were all attacked and had to be renewed.
There is little to be noted about the mental qualities of worms. They have been seen to be timid creatures. Their eagerness for certain kinds of food manifestly shows that they must enjoy the pleasure of eating. So strong is their sexual passion that they overcome for a time their dread of light. They seem to have a trace of social feeling, for they are not disturbed by crawling over each other’s bodies, and they sometimes lie in contact. Although remarkably deficient in the several sense-organs, yet this does not necessarily preclude intelligence, for it has been shown that when their attention is engaged they neglect impressions to which they would otherwise have attended, and attention, as is well known, indicates the presence of a mind of some kind. A few actions are performed instinctively, that is, all the individuals, including the young, perform each action in nearly the same manner. The various species of Perichæta eject their castings so as to construct towers, and the burrows of the Common Earth-worm--_Lumbricus terrestris_--are smoothly lined with fine earth and often with little stones, and the mouth with leaves. One of their strongest instincts is the plugging up of the mouths of their burrows with various objects, the very young worms acting in a similar manner. But some degree of intelligence is manifested, as will subsequently appear.