STUDIES ON BIOLOGY OF FRESHWATER MUSSELS. 22Q 



ly, for no stomachs nor intestines were found to contain larger 

 fragments than usually occur there. 



(c) Forced Feeding. 



From the above experiments, and on grounds discussed else- 

 where (p. 227), it is seen that the ingesting apparatus exercises 

 considerable choice, and that (at least under experimental condi- 

 tions) only certain sorts of material are admitted to the stomach. 



An attempt was made to introduce distasteful matter into a 

 starved mussel with the food. When fed alone, carmine had 

 never been ingested. It was therefore administered with Glcco- 

 capsa and macerated Spirogyra. In no case was it found in the 

 alimentary canal. Very little of the food entered, for thai matter. 

 The presence of the carmine caused a rejection of most of the 

 food as well. 



In order to ascertain if substances rejected by the mouth might 

 yet have the power to stimulate the secretion of the crystalline 

 style, these were introduced little by little through a fine pipette 

 directly into the stomach. Fine carborundum (120-180 gauge) 

 carmine, and starch were tried. In none of these cases was any 

 trace of a style to be found later. It should be explained that the 

 shock of operation was not alone responsible for this failure, for 

 when Glococapsa was fed to the animals in the same way, it was 

 capable of renewing the style to a slight degree. There is suffi- 

 cient ground for the conclusion that mere mechanical stimulation 

 of the intestine or style sac on the part of fine particles is not 

 sufficient to initiate the formation of the style. There must be a 

 stimulus of a chemical nature as well. A reaction to the feeding- 

 activity might have incited secretion through reflexes from the 

 palps. Yet this is inadequate to account for the renewal of the 

 style when Glccocapsa was administered through the stomach wall. 



(d) The Effect of Temperature on Style Renewal. 



With the approach of winter it becomes more and more diffi- 

 cult to secure a prompt renewal of the crystalline style on the 

 resumption of feeding. Where experiments are made in water 

 of quite low temperature the same behavior is observed. Riddle, 



