290 GILBERT C. BOURNE. 



diameter^ and is evidently undergoing dissolution. It can- 

 not at one and the same time be losing material and receiving 

 additions from the substance which has been called the 

 cuticle or tlie " fleche tricuspide." My interpretation is that 

 the crystalline style is added to at its hinder end, and that 

 the material for its reuewal is carried down the caecum by 

 the ciliated groove. List (10) has given an interesting 

 account of the formation of the crystalline style in specimens 

 of Mytilus fed with Indian ink, which is not inconsistent 

 with my suggestion. He does not, however, appear to have 

 subjected the style to the same careful chemical analysis as 

 Mitra. 



The numerous follicles of the liver are formed of two kinds 

 of cells. Large, coarsely-granular, clear cells with distinct 

 nuclei, and wedged in among the outer ends of these a smaller 

 number of deeply-staining, finely-granular cells resembling 

 the demilune cells of mixed salivary glands of mammals. 



The intestine, in the first part of its course where it is of 

 narrow calibre, with four ridges projecting into its lumen, is 

 lined by an epithelium consisting of attenuated ciliated cells 

 with deeply-staining, densely-crowded nuclei, among which 

 are a few goblet cells, smaller, and with more finelj^-granular 

 contents those occurring in the stomach. In the loop of the 

 intestine the ridges die out, the goblet cells disappear, and 

 the attenuated ciliated epithelium alone remains. In the 

 straight part of the intestine this is replaced by a columnar- 

 ciliated epithelium with a clear, somewhat granular cytoplasm 

 and pale oval nuclei containing a sparse chromatic reticulum 

 (fig. 24). There are no gland cells in this region, but the 

 cytoplasm of the epithelial cell stains bluish-green in picro- 

 indigo-carmine, and is very distinct from the section of the 

 intestine preceding it and from the proctodooum. It is usual 

 to call this part of the intestine the " rectum." But it is so 

 sharply marked off from the terminal portion of the alimentary 

 tract that I prefer to describe it as the large intestine, and 

 to restrict the name rectum to the short, somewhat enlarged 

 section of the gut which opens to the exterior by the anus 



