STUDIES ON BIOLOGY OF FRESHWATER MUSSELS. 22 7 



to throw light upon the actual stimulus which initiates the renewal 

 of the style. The stimuli may be either mechanical or chemical. 



Carborundum, carmine, starch, etc., of varying fineness, were 

 introduced into the incurrent siphon with the streaming water. 

 Such organic or inorganic material, however neutral, of whatso- 

 ever dilution, or however administered through the respiratory 

 water, were never found subsequently in the alimentary canal. 

 Nor did the molluscs ever display any indication of style renewal 

 in response to these things. The experiment has a further 

 significance to be discussed on page 229. 



A culture of Glccocapsa was looked over carefully and found 

 to have very few organisms of the size of Glccocapsa, but much 

 coarse debris. This material was washed into a jar with active, 

 starved mussels, and agitated from time to time to prevent its 

 settling. After eighteen hours the mussels were examined. The 

 crystalline styles were partially renewed in all cases. In others 

 kept in jars of Glccocapsa not stirred frequently the styles failed 

 to show any indications of re-forming, even after three or four 

 days. Evidently not enough food to stimulate style formation 

 had been taken into the siphons. In all, small masses of Glccocapsa 

 were encountered in the rectum, in the stomach, and in clots of 

 mucus upon the gills and palps. The clots were almost pure 

 Glccocapsa. The stomach and intestine contained minute frag- 

 ments of green, partially digested individuals, and sometimes 

 Glccocapsa cells without the capsule. There is thus no doubt but 

 that a pretty rigid selection of the alga from the coarser matter 

 with it was taking place, and that the alga was being digested. 



The frequent occurrence of the Glceocapsa in the rectal con- 

 tents, still wrapped in mucus, shows the effect of the want of 

 the style. Had that organ been present the mucus masses would 

 probably have been torn up, the alga freed in the stomach and 

 exposed to digestive action. It appears that the process of di- 

 gestion does not function perfectly, even prior to the formation 

 of a style, and not even a hungry mussel exposes all particles 

 equally well to the digestive fluids. 4 



4 Edmondson finds the alimentary tract of Mya arenarla empty of food 

 until the style is partially replaced. 



