PROGRESS IN BIOLOGICAL INQUIRIES 61 



spects from the intestinal amebae found in other animals. One of its 

 most strikinjx characteristics is the formation of multinucleate cysts, 

 which ma}^ grow and divide while in the lumen of the stomach 

 and intestine. The extraordinary life history of this species in 

 the trout has been worked out and the results are now ready for 

 publication. 



An interesting trout parasite and one that may be of considerable 

 economic importance was found in a specimen of golden trout from 

 the Mount Shasta region in California. This fish was one of a 

 number that died at the Steinhart Aquarium, San Francisco, and 

 was infected with a myxosporidian belonging to the genus Myxidium. 

 This genus is common in the gall bladder of fishes, but usually is 

 not injurious. The parasite was very abundant in the bile ducts 

 of the liver, causing a severe hypertrophy of the ducts, which evi- 

 dently resulted in the death of the host. It is obvious that e^•ery 

 precaution should be taken to prevent the introduction of tliis 

 parasite into our hatcheries, where it might cause very serious 

 injury. 



An investigation of the so-called soft-egg disease was under- 

 taken at the request of the Eastern Trout Growers' Association. 

 During the last iew years this disease has caused serious losses at a 

 number of commercial trout hatcheries in New England. The 

 trouble does not appear until some time after the eggs are laid, when 

 they become soft and flaccid and a portion of the yolk may be ex- 

 truded. During NoAxmber M. C. James visited several of the hatch- 

 eries where the disease was most serious and brought back a quan- 

 tity of infected eggs for further study. It was determined that the 

 trouble is due to small openings Avhich are formed in the egg mem- 

 brane by some organism. These openings allow the water to pass 

 freely in and out of the egg. thus destroying the turgidity character- 

 istic of normal eggs. It is evident that the holes in the membrane 

 are formed from the exterior, but it has not yet been possible to de- 

 termine definitely what organism is the primary cause of the trouble, 

 since several species of bacteria and a species of ameba are almost 

 invariably present. It is planned to continue the investigation of 

 this disease during the next spawning season. 



PHYSIOLOGY AND NUTRITION OF FLSHES 



Feeding experiments on the addition of vitamins to trout foods 

 were continued during the past summer. The principal experiments 

 were conducted by M. C. James, under the direction of Dr. H. S. 

 Davis, at the White Sulphur Springs (AY. Va.) station, and in gen- 

 eral the results were in complete accord with those obtained at the 

 Manchester (Iowa) station during the summer of 1923. It was 

 found that the addition of cod-liver oil and yeast to beef heart 

 noticeably increased the growth, but an even more important result 

 was the marked decrease in the mortality. In most instances the 

 mortality among fish fed heart to which a small quantity of yeast 

 and oil had been added was less than one-half that among the fish 

 fed a straight heart diet. One of the most important results of the 

 season's work was the discovery that only very small amounts of oil 

 and yeast are required and that the addition of 1.5 per cent of oil 



