PROGRESS IN BIOLOGICAL INQUIRIES, 19 33 377 



In the bottom survival c\\i)i'riinc'nts tlio yellow sandshell was 

 found to be the least resistant to siltinj^- in, and the river mucket 

 from Indiana, the most resistant, of the better commercial species. 

 The best survival (considering the heavy-shelled species) against the 

 unfavorable conditions brought about by silt deposit was made by 

 the maple-leaf shell. 



Mv^sel crate experhients. — From the results of the bottom sur- 

 vival experiments it was evident that in view of the average volume 

 of water available for such raceways, it was not feasible to raise 

 mussels in large enough numbers on the bottom to make the project 

 commercially practical, especially with the silt hazard always an 

 uncertain variable. With a view to eliminating the bottom silt 

 hazard and also to increasing the actual number of mussels held in 

 any raceway to a commercially desirable figure, crates in which 

 mussels are now being raised, were devised for the raceways In 

 these crates the mussels are relatively free from any sort of mud or 

 silt hazard and as the trays of the crates are in tiers, from 3 to 10 

 times as many mussels are now being carried in a single crate as 

 could be raised in the same bottom space as that supporting the 

 crat€. This advantage is gained too without any increase in the 

 amount of water used. During 4 months of trial, the crates, of 

 which we now have 3 types, are proving very successful, and the 

 survival of the mussels in the crates has been excellent even though 

 the animals are being crowded intentionally to determine the maxi- 

 mum number a given volume of water will support, both with and 

 without artificial feeding. The effects of light penetration through 

 the water on the animals in the top trays, the spread of mites, and 

 the growth of algae on the trays are being followed simultaneously 

 with the main experiment, and at present over 10,000 mussels are 

 being carried in one series of crates alone in species survival, breed- 

 ing stock, and age-class tests. 



physiological and hiocheTnical studies of mussels. — In order to 

 determine the success of various tests in the Fort Worth raceway 

 project, as well as the condition of the mussels themselves, several 

 lines of physiological and biochemical studies on mussels have been 

 followed of necessity at the Columbia laboratories. 



Food and food storagre. — The feeding experiments have been con- 

 tinued at Columbia. The ability of mussels to utilize various types 

 of cheap material as food was determined by biochemical analyses 

 of the stored food. The relation of this stored food to survival and 

 to the body condition of the mussel has just been checked in a series 

 of experiments running over some 18 months. It was found that 

 the yellow^ sandshell could survive complete starvation for 10 to 18 

 months before the reserve food supply was seriously depleted, if the 

 animal were well fed to start with. The mussel seems to be an ir- 

 regular feeder, storing large quantities of reserve food when food 

 is abundant and easily available. 



Reproduction. — So little is known concerning the breeding habits 

 of most of the species of fresh-water mussels that various difficulties 

 have been encountered in obtaining breeding stock for propagation 

 and in selecting lines from which to raise mussels. Both at Columbia 

 and Fort Worth test series are being held for reproduction studies, 

 and attention is given to this phase of the work in the field. 



