PROGRESS IN BIOLOGICAL INQUIRIES, 1924 43 



footh increased growth and lowered mortality over the liver, oil, and 

 3'east diet. 



These experiments, on a more extensive scale, are being continued 

 during the summer of 1924 at the White Sulphur Springs (W. Va.) 

 station, and the results to date are in complete accord with those of 

 the Manchester experiment. Similar experiments with both finger- 

 ling and brood fish under ordinary hatchery conditions have also 

 been undertaken at the Erwin (Tenn.) and Wytheville (Va.) sta- 

 tions. As a result of these experiments it is believed that by the end 

 of the season it will be possible to prescribe a diet distinctly superior 

 to those now in use at the various trout hatcheries. 



For a number of years investigations in the physiology and nutri- 

 tion of fishes and other aquatic animals have been carried on in co- 

 operation with the University of Wisconsin. During the year Dr. 

 W. A. Kenyon has completed a study of the digestive enzymes of 

 representative fresh-water fishes. The carp, which has no stomach, 

 shows no evidence of peptic digestion. The enzymes of fishes are 

 found in general to have the greatest digestive action at about the 

 same temperature as in mammals. 



Prof. A. S. Pearse and Miss A. L. Hintze have for a year fed tur- 

 tles on certain natural foods and on synthetic rations of pure foods. 

 Painted turtles, gophers, and terrapins were kept in steam-heated 

 tanks. The foods used were lettuce, eg^, meal worms, and mixtures 

 of dextrin, casein, cod-liver oil, yeast, salts, and sand. Each turtle 

 was weighed weekly. Individuals fed on ''complete" rations rarely 

 died and showed marked increases in weight. It is believed that 

 satisfactory data on the rate of growth of turtles of different ages 

 has been obtained. The lots fed on rations that were deficient in 

 vitamines showed a higher rate of mortality and did not grow, or 

 lost weight. Dr. S. Lepkovskv is now making chemical analyses of 

 all the turtles that were used during the feeding experiments. 



E. S. Hathaway is investigating the relation of temperature to the 

 metabolism of fishes and other aquatic animals. Data have been 

 accumulated on the ability of fishes of various ages to withstand 

 changes in temperature, the amount of food eaten, oxygen consump- 

 tion, and carbon-dioxide output. Younger fishes are found to 

 possess wider ranges of tolerance and greater powers of adjustment 

 than older individuals. Species that range through a variety of 

 habitats apparentlj'' have greater ability to endure extreme varia- 

 tions. In general, the amount of food consumed is greater at higher 

 temperatures, up to about 30^ C. 



EXPERIMENTAL WORK IN FISH CULTURE 



Experiments in the culture of seven species of fish have been con- 

 ducted at the Fairport station during the year. 



Both the lake sturgeon, Acipejiser ruhicundus, and the shovel- 

 nose sturgeon. Scaphirhynchus platj/rhijnchus^ were given consider- 

 able study with the object of developing a method of culture for 

 them. Attempted pond culture of the shovelnose sturgeon in one 

 of the station's ponds did not prove successful, but was considered 

 worth repeating with modifications to more closely approximate 

 natural conditions. 



