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Show 46 HABITS OF WORMS. CII4-P. I. three larger, or a single very large concretion of carbonate of lime, as much as ll mm. in diameter. When a gland includes only a few very small concretions, or, as sometimes happens, none at all, it is easily overlooked. The large concretions are round or oval, and exteriorly almost smooth. One was found which filled up not only the whole gland, as is often the case, but its neck; so that it resembled an olive-oil flask in shape. These concretions when broken are seen to be more or less crystalline in structure. How they escape frorn the gland is a marvel ; but that they do escape is certain, for they are often found in the gizzard, intestines, and in the castings of worms, both with those kept in confinement and those in a state of nature. Claparede says very little about the structure of tbe two anterior glands, and he supposes that the calcareous matter of which the concretions are formed is derived from the four posterior glands. But if an anterior gland which contains only small concretions is placed in acetic acid and afterwards dissected, or if sections are made of such CHAP. I. CALCIFEROUS GLANDS. 47 a gland without being treated with acid, lamel1re like those in the posterior glands and coated with cellular matter could be plainly seen, together with a multitude of free calciferous cells readily soluble in acetic acid. When a gland is completely filled with a single large concretion, there are no free cells, as these have been all consumed in forming the concretion. But if such a concretion, or one of only moderately large size is dissolved in acid, much membranous matter is left, which appears to consist of the rem~dns of the formerly active lamellre. After the formation and expulsion of a large concretion, new lamellre must be developed in some manner. In one section made by my son, the process had apparently commenced, although the gland contained two rather large concretions, for near the walls several cylindrical and oval pipes were intersected, which were lined with cellular matter and were quite filled with free calciferous cells. .A. great enlargement in one direction of several oval pipes would give rise to the lamellro. Besides the free calciferous cells in which no nucleus was visible, other and rather |
