PROGRESS IN BIOLOGICAL INQUIRIES, 1931 525 



and Tennessee, to the production of artificial beds in controlled habi- 

 tats has made necessary extensive studies on the i^hysiology of the 

 fresh-Avater mussel, particularly feeding and p;eneral reactions, be- 

 cause of the paucity of literature on these subjects bearing on the 

 particular problems in hand. Consequently, mussels from various 

 parts of the United States have been placed under observation in 

 the laboratories of the unit at Columbia, Mo., and detailed physio- 

 loirical observations made on the movements, respiration, heart action, 

 feeding-, hibernation, and growth of these animals. From these 

 studies the oxj'^gen requirements, food choices, food elaboration, and 

 winter habits of these animals have been followed preparatory to 

 placing them under observation in the controlled habitats out of 

 doors. Work reported last year has been confirmed, namely, that 

 contrary to the popular belief most of the mussels prefer clean water 

 and are very sensitive to changes in their environment, particularly 

 such changes as are produced by erosion, silt, sewage pollution, and 

 industrial wastes. It has been found that the animals can be fed 

 readily with several inexpensive substances and the general condition 

 of the mussel improved, as shown by physiological observations on 

 the activity of the animal itself and by the amount of food stored in 

 the living animal. All of these laboratory observations are to be 

 used as scientific backgrounds for the field work at the propagation 

 station. 



Observations on glochidia and spawning time of several species of 

 fresh-water mussels have been extended during the past year. The 

 peculiar spawning habits of the Arkansas fanshell have been worked 

 out in considerable detail and constitute a unique type in the known 

 methods of spawning of fresh-water mussels. Gravid yellow sand- 

 shells have been carried throughout the winter and observations on 

 the needs of gravid individuals made to extend the knowledge of 

 handling of these animals for breeding stock. 



A census of the parasites, diseases, and injuries of the fresh-water 

 mussels have been carried on through the year, as all parasites found 

 have been preserved and the physiological and pathological condi- 

 tions of each mussel studied noted. As is well known, a water mite 

 is perhaps the commonest parasite of fresh-w^ater mussels in the 

 United States, and the depredations of this parasite have been fol- 

 lowed in the field work throughout the year. 



Limnological observations. — Various species of animals have been 

 used as incticators of river conditions, and consequently collections of 

 plankton, shore animals, and bottom forms have been made wherever 

 possible throughout the course of the field work. These collections 

 are discussed in the forthcoming report on the 1931 survey. 



ACTIVITIES OF THE FISHERIES BIOLOGICAL LABORATORIES 



AVOODS HOLE, MASS. 



The bureau's laboratory at Woods Hole, under the direction of 

 O. E. Sette, has furthered the scientific investigations of the bureau 

 in supplying facilities for experimental work on oyster problems, fish 

 tagging, rate of development of mackerel eggs, and rearing of larval 

 fish. The station also served as a base for the collection of data on 

 the local mackerel fishery; for studies on planktonic fish e;rgs and 



