2l8 WILLIAM RAY ALLEN. 



t 



action, but has the shelter of a broad zone of Potamogeton. The 

 creek water was from the mouth of Pocahontas creek, having a 

 depth from a few inches up to more than a foot, and a bottom of 

 gravel and rubble. A drain from a large septic tank enters 500 

 feet upstream. In its upper course it receives the water of 

 drainage ditches in swamp land, and has a small, though constant, 

 volume throughout summer. Its flow is rapid, and the character 

 of the bottom such that mussels have not ascended it. The water 

 has a slightly brown color due to its swampy course (Rice, '16). 



In this experiment two mussels were used as checks, three 

 kept in filtered water, ten placed in the overflow from the plank- 

 ton net, and ten were fed upon the gross concentrate given them 

 in tap water. 



Of the two checks, one developed a well formed crystalline 

 style, the other none, but it had a large amount of green ma- 

 terial in the intestine, showing that it also had resumed feeding. 



Of the ten fed upon net plankton, seven renewed the style 

 more or less completely, three not at all; of the naiiiioplaiikton- 

 fed eight had formed a style and two had not. These data are 

 not full, yet they demonstrate the ability of the respective food 

 materials to renew the style. 



It will be seen that there is little difference in the power to 

 renew the style between the larger plankton which remained, and 

 the smaller which went through the silk. It is certain that the 

 larger forms do have a food value, for there were few of the 

 smaller which remained in the plankton bucket, and the residue 

 of grosser material alone \vas put into the aquarium with the 

 first group of mussels. It is possibly not quite so well demon- 

 strated that the other eight renewed the styles in response to 

 the ingestion of nannoplankton solely, but such is a reasonable 

 supposition. Two things at least cannot be gainsaid : ( i ) there 

 was a significant increase in the ratio of megaloplankton to nan- 

 noplankton within the bucket, and of course a reversal of this 

 ratio outside, without greatly affecting the crystalline style re- 

 newal in either case; (2) no net plankton \vas recognized in the 

 intestines of the second group of experimental animals, although 

 conspicuous in those used as a check. 



The above facts do not argue a greater digestibility of the 



