454 E. RAY LANKESTER. 



position, the use of alcohol must be avoided since the pigment 

 is dissolved by that preservative. It is, however, insoluble in 

 formol. 



Claparede, in his 'Annelides Sedentaires/ has described 

 the pigmentation of the epithelium of this region of the in- 

 testine. A careful examination, by teazing fresh material and 

 also by sections of material preserved in formol, shows, ac- 

 cording to Benham's observations, that the pigment occurs 

 solely in the form of spherical corpuscles varying in size 

 (fig. 4), and embedded in the protoplasm of the epithelial 

 cells (fig. 3). These granules are not dissolved by alcohol 

 entirely, but a colourless, oily-looking stroma, quite structure- 

 less and translucent, of the same shape as the original coloured 

 granule, is left in the cell-body. 



Claparede speaks of the pigment in the intestinal wall as 

 "hepatic" pigment. Joyeux-Laffuie ('Archives de Zoologie 

 Experim.,^ 1890) gives a detailed account of the distribution 

 of the pigment-bearing cells in the intestinal wall ; he figures 

 the cells and terms them " cellules biliaires.^' Dr. Benham 

 distinguishes the elongated ciliated cells which contain the 

 green granules from other associated " gland-cells,^' of which 

 there appear to be two varieties. 



It is evident that the terms " hepatic pigment" and ''bile- 

 cells" are not open to the same objection when applied to 

 these cells of the enteric epithelium, as when applied, accord- 

 ing to the custom of writers of forty years ago, to the brown- 

 coloured tunic of the earthworm's intestine, now often called 

 the "chloragogenous" tunic or cells. The pigmented cells of 

 the intestine of Chaetoplerus are really of enteric origin, as is 

 the hepatic gland in Vertebrates, whilst on the other hand the 

 chloragogenous tunic is part of the coelomic epithelium. 



It is impossible to suppose, in view of the fact that Chaeto- 

 pterus lives buried in the sand in a large parchment-like tube, 

 that the intestinal pigment can have any function as pigment. 

 On the other hand, it is not unlikely that it may eventually be 

 shown that this green fluorescent " Chsetopterin" is really re- 

 presentative of the biliverdin of Vertebrate bile. 



