BULLETIN. OF THE UNITED STATES FISH COMMISSION. 191 



die fungus, showing apparently tbat the acid was not the cause of its 

 death. 



Mr. Livingston Stone has recommended the use of a strong solution 

 of common salt to kill fungus, which he has found quite effectual. Mr. 

 Behler, of the Druid Hill hatching house, says a saturated solution of 

 salt water is effectual; and he also states that if young salmon infested 

 with the fungus are dipped bodily into asphalt, the fungus will be killed 

 and the young fish come out all right and healthy, the asphalt gradually 

 peeling off of their bodies. This last statement seems almo.-t incredible, 

 but it has been stated to me in good faith by the experimenter himself. 



y. DISTURBANCE OF THE BALANCE OF CONDITIONS, AND ITS INFLU- 

 ENCE ON THE CRUSTACEAN FOOD OF THE SHAD. 



In conducting the experiment of feeding the young shad, vast num- 

 bers of minute Daphnida? were caught, which were put in the glass 

 aquaria with the young fish; sometimes the number of these minute 

 crustaceans captured at one time was so great that when closely packed 

 they would almost equal a solid quart in bulk. Great mortality was no- 

 ticed among them soon after beiug placed in the aquarium with the 

 fish, which would indicate that they had been subjected to a fatal 

 change of surroundings. Various reasons might be assigned as prob- 

 able causes of this mortality. It may be that the rapid circulation of 

 water in the aquarium was one of them, or it may be supposed that 

 when taken from the stagnant water of the carp pouds and transferred 

 to water of a considerably lower temperature in the hatching house 

 the change was too great. A still more probable cause may be the fact 

 that the crustaceans, when removed from amongst the water plants in 

 the pond, were deprived of their natural food, and as a result starved to 

 death. 



Whatever may have been the cause of this phenomenon, however, we 

 may be assured of this fact, that in supplying live food to shad larva? 

 we must also be careful to attend to the vital conditions required by 

 the former. If it is desired to keep this liviug food in a healthy state, so 

 as to multiply in the aquaria, it is probable that water plants must be 

 supplied for the purpose of furnishing the requisite conditions for the 

 l>rotection and multiplication of the food of the living shad-food. Un- 

 til recently we have not been able to supply quite the proper conditions 

 for the nutrition of the young shad, and in feeding the latter it becomes 

 evident that we must take care to feed the food, which may be done 

 by providing the conditions for the propagation of protozoa, alga?, &c, 

 in the aquaria or shad nurseries. 



VI. — A MEANS OF DEMONSTRATING- CARTILAGE IN FISH EMBRYOS. 



Knowing the potency of potassic hydrate in dissolving protoplasm, it 

 occurred to me to try its efficiency as a means of getting rid of the tis- 

 sues and membranes which envelop the trabecule cranii, hyoid, and 



