CuAP. I. CALCIFEROUS GLANDS. 45 



are immersed iu 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. After a 

 very large number have been dissolved, a 

 flocculent residue is left, which apparently 

 consists of the delicate ruptured cell-walls. 

 In the two posterior pairs of glands the 

 carbonate of lime contained in the cells oc- 

 casionally aggregates into small rhombic 

 crystals or into concretions, which lie be- 

 tween the lamellae ; but I have seen only one, 

 and Claparede only a very few such cases. 



The two anterior glands differ a little in 

 shape from the four posterior ones, by being 

 more oval. They differ also conspicuously in 

 generally containing several small, or two or 

 three larger, or a single very large concre- 

 tion of carbonate of lime, as much as I2 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 ai'e 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 



