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Quarterly Journal of Microscopical Science, Vol s3-97, 421-427, Copyright © 1956 by Company of Biologists
1 Department of Zoology, King's College, Newcastle upon Tyne. Present address, Department of Zoology, British Museum (Natural History), London, S. W. 7.
Descriptions of the calcium-secreting glands, which produce the calcareous component of the tubes, are given for Spirorbis, Hydroides, and Serpula. In Hydroides the gland is a simple tubule. The gland in Spirorbis is tubular but the gland-cells have unusual extensions which project into the lumen. In the centre of these extensions there is always a strongly basiphil substance. In Serpula the glands are tubulo-racemose or compound tubular, similar to those in Pomatoceros.
In addition to the calcium-secreting glands in Serpula there are two ventral calcium sacs in the posterior part of the peristomium which secrete calcareous material. The sac wall has a peculiar structure, being non-cellular and consisting of two layers, one basiphil the other acidophil. In the acidophil part two layers are seen, one fibrous and the other optically homogenous in which numerous small bodies are found.