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Show 50 HABITS OF WORMS. CIIAP. I. h ave l:1 een 1e n 0 w n to contain as much as 72 per cent. of Hme. Worms therefore would be liable to become charged with this ear~h, 1 th ere Sun ess ere w ome sp-ecial means for 1ts excre t1. on; and the calciferous glands are well adapted for this purpose. The worms which live in mould close over th~ chall~, f h . tl1e1·r intestines filled w1t h tins o ten ave · . substance, and their castings are almost white. Here it is evident that the supply of cal-car eo us matter must be superabundant. Nevertheless with several worms collecte~ on such a site, the calciferous glands contamcd as many free calciferous cells, and f~1ly as many and large concretions, as d1d the o-lands of worms which lived where there was little or no lime; and this indicates that the lime is an excretion, and not a secretjon poured into the alimentary canal for some special purpose. . . , . On the other hand, the following considera-tions render it highly probable that the carbonate of lime, which is excreted by the glands, aids the digestive proces~ und~r ordinary circumstances. Leaves dunng theu decay generate an abundance of various kinds CITAP. I. CALCIFEROUS GLANDS. 51 of acids, which have been grouped together under the term of humus acids. We shaH have to recur to this subject in our fifth chapter, and I need here only say that these acids act strongly on carbonate of lime. The half-decayed leaves which are swallowed in such large quantities by worms would, therefore, after they have been moistened and triturated in the alimentary canal, be apt to produce such acids. And in the case of several worms, the contents of the alimentary canal were found to be plainly acid, as shown by litmus paper. This acidity cannot be· attributed to the nature of the digestive fluid, for pancreatic fluid is alkaline; and we have seen that the secretion which is poured out of the. mouths of worms for the sake of prepanug the leaves for consumption, is likewise alkaline. The acidity can hardly be due to uric acid, as the contents of the upper part of the intestine were often acid. In one case the contents of the gizzard were slightly acid, those of the upper intestines being more plainly acid. In anotller case the contents of the pharynx were not acid, those of the gizzard doubtfully so, while tlwse of the jn- E 2 |