not only the contents of the intestines, but their ejected matter or the castings are generally acid. The digestive fluid of worms resembles in its action, as already stated, the pancreatic secretion of the higher animals, and in these latter pancreatic digestion is necessarily alkaline, and the action will not take place unless some alkali be present; and the activity of an alkaline juice is arrested by acidification, and hindered by neutralization. Therefore is seems probable that innumerable calciferous cells, which are emptied from the four posterior glands in the alimentary canal, serve to neutralize more or less completely the acids generated there by the half-decayed leaves. These cells, as has been seen, are instantly dissolved by a small quantity of acetic acid, and as they do not always suffice to render of no effect the contents of the upper part of the alimentary canal, it is probable that the lime is aggregated into concretions, in the anterior pair of glands, in order that some may be conveyed to the posterior parts of the intestine, where these concretions would be rolled about among the acid contents. The concretions found in the intestines and in the castings often present a worn appearance, but whether due to attrition or chemical corrosion it is impossible to say. That they are formed for the sake of acting as mill stones, as Claparède believed, and of thus assisting in the trituration of food, is not at all likely, as this object is already attained by the stones that are present in the gizzards and intestines. In dragging leaves into their burrows worms generally seize the thin edge of a leaf with their mouths, between the projecting upper and lower lip, the thick and strong pharynx at the same time being pushed forwards within their bodies, so as to afford a _point de resistance_ for the upper lip; but in the case of broad and flat objects the pointed anterior extremity of the body, after being brought into contact with an object of this kind, is drawn within the adjoining rings, so that it becomes truncated and as thick as the rest of the body. This part is then seen to swell a little, seemingly from the pharynx being pushed a little forwards. By a slight withdrawal of the pharynx, or by its expansion, a vacuum is produced beneath the truncated, slimy end of the body whilst in contact with the object, and by this means the two adhere firmly together. Worms can attach themselves to an object in the same manner under the water. [Illustration: COMMON EARTH-WORMS. Out on a Foraging Excursion.]