CHAPTER III 



CALCIFEROUS GLANDS 



Although the alimentary canal is virtually a straight tube with 

 but little specialization in its structure, save in the muscular 

 triturating gizzard, there are in most oligochaetes various glands 

 associated w^ith the gut. Some of these were mentioned in the last 

 chapter concerning digestion. The most prominent of these 

 glandular structures, the calciferous glands, were only briefly 

 mentioned and it is here intended to deal with them more fully. 



These glands occur as pouch-like diverticula somewhere along 

 the length of the oesophagus, e.g. segments 1 1 and 12 in L. terrestris 

 with an associated oesophageal pouch in segment 10. Within these 

 pouches the epithelium is greatly lamellated or folded. The whole 

 structure is very well provided with blood vessels, the blood 

 flowing through them having come from the absorptive intestine 

 posteriorly. The general gut blood sinus is interposed between the 

 two layers of the lamellae (Fig. 9), A detailed account of the 

 structure of these glands is to be had from Stephenson (1930). 



As the name calciferous glands suggests the cells that line these 

 diverticula are glandular in nature and they secrete calcium car- 

 bonate. They undergo cycles of activity forming, first, globules 

 in the cytoplasm which, secondly, give rise to spicules of calcium 

 carbonate and these, thirdly, amalgamate to form irregular masses 

 (Bevelander and Nakahara, 1959). These concentrations of 

 calcium carbonate are released into the lumen of the glands and 

 pass from there into the gut. It has, however, recently been 

 suggested (van Gansen, 1959a) that this is not the only method of 

 forming calcareous bodies in the gland. By a method described 

 later (p. 34) the fluid contents of the interior of the gland are 

 concentrated until the calcium carbonate precipitates out in the 

 lumen of the gland without ever being in solid form in the cells of 

 the gland. 



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