106 • THURLOW C. NELSON 



the surface of the cells; thh'd, the streams of food and foreign 

 mattfer entering from the oesophagus are largely composed of 

 heavy mucus secreted by the gills and palps, and this is in 

 sufficient quantity and of a consistency capable of acting as a 

 protective covering if such were needed; fourth, an examination 

 of the pellets of sand passed down the intestinal groove of 

 Modiolus shows them to be composed of sand grains compactly 

 held together by a small amount of thick mucus, such as that 

 secreted by the body surface or oesophagus. 



A second function of the crystalline style, though probably a 

 minor one, has been referred to above (p. 83) in describing the 

 formation of the style, where it was shown how undigested food 

 materials, passed down the intestine along with the waste matter, 

 are caught and incorporated into the inner core of the style. 



During the winter I have found individuals in which practi- 

 cally the entire style was composed of the brown particles which 

 form so large a part of the alimentary mass of the stomach. The 

 crystalline style thus serves incidentally, except in those forms 

 in which it lodges in a separate caecum, as a means of restoring 

 to the stomach nutriment which might otherwise be lost. 



One is greatly tempted at this point to consider the endo- 

 style of Amphioxus, in so far as it acts in the transfer of food, 

 as possibly an analogous structure. However, as I have been 

 unable to examine living specimens of this animal, this simi- 

 larity is merely suggested here. 



Finally, we have seen that the crystalline style of the lamelli- 

 branchs contains a very active amylolytic ferment, as was first 

 held by Coupin ('00), followed by Mitra ('01), van Rynberk 

 ('08) , and others. From the evidence presented by these workers, 

 together with the facts shown in this paper, it is probable that 

 the enzyme is held in a viscous matrix of a mucin-like substance 

 which gives the reactions of a globulin. 



Since the food of the majority of lamellibranchs consists 

 mainly of unicellular plants, and since these animals have no 

 salivary secretion, an abundant supply of starch-splitting en- 

 zymes in the alimentary canal is a necessity. 



