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Show 44 HABrrs OF WORMS. CHAP. I. verted into peptone not within a stomach, but on the surfaces of the leaves. Calc~ferous Glands.-These glands (s~e Fig. 1), judging from their size and from the1r rich supply of blood-vessels, must be of much irnportance to the animal. But almost ~s many theories have been advanced on thmr use as there have been observers. They consist of three pairs, which in the common earth-worm debouch into the alimentary canal in advance of the gizzard, but posteriorly to it in Urochtooa and some other genera.* The two posterior pairs are formed by lamelloo, which according to Claparede, are diverticula from the oosophagus.t These lamelloo are coated with a pulpy cellular layer, with the outer cells lying free in infinite numbers. If one of these glands is punctured and squeezed, a quantity of white pulpy matter exudes, consisting of these free cells. They are minute, and vary in diameter from 2 to 6 JL· They contain in their centres a * Perrier,' Archives de Zoolog. exp6r.' July, 1874, pp. 416, 419. t 'Zeitschrift flir wisscnscbaft. Zoologic,' B. xix. 1869, PP· 603-606. CHAP. I. CALCIFEROUS GLANDS. 45 little excessively fine granular matter; but they look so like oil globules that Claparede and others at first treated them . with ether. This produces no effect; but they are quickly dissolved with effervescence in acetic acid, and when oxalate of ammonia is added to the solution a w bite precipitate is thrown down. vVe may therefore conclude that they contain carbonate of lime. If' the cells are immersed in a very little acid, they become more transparent, look like ghosts, and are soon lost to view; but if much acid is added, they disappear instantly. ..A . fter a very large number have been dissolved, a flocculent residue Js left, which apparently consists of the delicate ruptured cell-walls. In the two posterior pairs of glands the carbonate of lime contained in tho ce1ls occasionally aggregates into small rhombic crystals or into concretions, which lie be· tween the lamellro; but I have seen only one, and Claparcde only a very few such cases. The two anterior glands differ a little in shape from the four posterior onos, by being more oval. They differ also conspicuously in generally containing several small, or two or |
