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the acids which are always generated during the decay of vegetable substances, whether 

 in the intestines of animals or on the ground ; and in this case it is probable that con- 

 cretions of lime are formed by some of the glands, so that they may be carried down to 

 the posterior parts of the intestine before they are dissolved. Claparede thought that 

 these hard bodies were formed to act as millstones, and thus aid in the trituration of the 

 food ; but as worms swallow many small stones, which may generally be found in their 

 gizzards, Darwin's theory is the more probable. 



Worms have no eyes, but yet are able to appreciate light by means of their nervous 

 system through their skins. If a strong light is turned on them suddenly they will some- 

 times dart back into their holes with great quickness. This is not always the case, 

 however, for if the anterior portion of the body is shaded, an intense light may be thrown 

 on the rest of the body without any notice being taken. A moderate light is after some 

 time generally observed by them, and they will retire to their holes slowly and apparently 

 hesitatingly. Darwin found that the colour of light made no difference in their appre- 

 ciation of it, and that a moderate radiant heat, such as that from a hot poker being held 

 near them, did not cause them so much emotion as a bright light. Worms being nocturnal 

 in their habits, an Appreciation of the difference between day and night is, of course, 

 useful to them, and this they possess. The sensitiveness to light is less when a worm is 

 engaged in eating or in dragging leaves into its burrow — a fact which Mr. Darwin is 

 disposed to consider analogous to what in higher animals we know as the distracting 

 influence of attention. It is a curious fact that worms kept in confinement keep quiet 

 during the day, and only crawl about and work at night. 



Although worms are deprived of vision and have no sense of hearing, their sense of 

 touch is most highly developed. In observing them the greatest care must be taken not 

 to jar the table or touch the jar in which they are, nor even to breathe on them, or they 

 will instantly retire to their holes. In watching them out of doors it is necessary to 

 tread very lightly or very little will be seen of their habits. A heavy footfall is sufficient 

 to send home all the worms for many yards around. This is doubtless the reason why 

 most of the birds which feed on worms are able to run and walk as well as hop. 



With regard to the sense of smell Mr. Darwin arrived at the interesting conclusion 

 that it was very feebly developed, and only at all for certain natural objects which were 

 suited for food. Pieces of cabbage, onions, the leaves of parsnips, celery and many other 

 plants were placed on the pots, and certain ones were always chosen and others left. 

 Worms appear to be omnivorous, bits of meat and fat were always taken and eaten as 

 well as enormous quantities of earth, out of which they extract any digestible matter, 

 they will eat sugar, liquorice and almost any other substances which are given them. 

 They are even cannibals, for they will eat the bodies of dead worms if they find them 

 lying near their burrows. It would appear that the leaves which they draw into their 

 holes are smeared with a fluid which is alkaline, and which acts on the starch and other 

 contents of the plant cells and very much hastens their decay, " it thus resembles in 

 nature the pancreatic secretion, and serves partly to digest the leaves before they are 

 taken into the alimentary canal — so constituting the only case of extra-stomachal 

 digestion hitherto recorded in an animal." In this way worms do good service by 

 quickly decomposing the dead leaves and mixing them with the soil, nor is this the only 

 way in which the surface soil is improved by these insignificant creatures, for Mr. 

 Darwin has shown by most careful experiments that what gardeners complain of so 

 bitterly, that the worms spoil the appearance of their carefully cut lawns by raising up 

 all over them the unsightly mounds "which we call worm-casts, they are of very great 

 importance to the agriculturist. For not only do worms, by sinking their burrows deep 

 into the earth, render it permeable by air and water, and so bring about its disintegra- 

 tion ; but they are most powerful and active agents in adding depth to the soil and in 

 covering up comparatively barren tracts with a layer of rich vegetable mould. Mr. 

 Darwin began his investigations by remarking two most striking characters possessed by 

 vegetable mould. These were, that it was of nearly a homogeneous nature throughout, 

 although overlying different kinds of subsoil, and the uniform fineness of the particles. 

 This is easily seen in a gravelly country where in ploughed fields there are many stones 

 visible, while in an adjacent pasture there will be no stones within some inches of the 



