182 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



be taken iu opening and closing it, and, in order to ventilate it, the open- 

 ing in the upper part of the chamber for the admission of air should be 

 provided with a filter of cotton -wool; (8) it would be necessary to scald 

 and sterilize new cotton cloths, since these are almost always laden with 

 germs. These precautions, observed with scrupulous care, would insure 

 success, as far as the danger from fungus is concerned, in conducting 

 this mode of retarding development. 



The second series of experiments were conducted at Washington in 

 association with Colonel McDonald, this gentlemen having kindly under- 

 taken to aid in the work of experimentation, by means of various in- 

 genious forms of small and convenient hatching apparatus, of his own 

 devising, mostly made of glass. The method pursued consisted partly 

 in treating the eggs for some time on the dry principle on trays, com- 

 pleting the incubation afterwards in the glass apjiaratus fed with water 

 from a coil of tin pipe k«pt under ice in a refrigerator ; this enabled us 

 to maintain the temperature of the water supply at a pretty constant 

 point, ranging from 60° to 63° F. It was necessary, on account of the 

 distance which the eggs had to be transported, to use trays covered 

 with damj) cloths on which the impregnated, water-swollen ova were 

 carried in transit from the spawning grounds. The experiments were 

 conducted in the basement of the Smithsonian Institution, where some 

 of the trays of eggs were placed in a refrigerator and others put directly 

 into the water at the temperature stated above, using the McDonald 

 apparatus. The results of these experiments were of great interest and 

 of considerable value, as giving us data for certain precautions to be 

 observed iu the conduct of future work and experimentation, as may be 

 learned from the account of them which foUows. 



Colonel McDonald found it necessary to devise some ready means of 

 transporting the ova from the spawning grounds over a score of miles 

 down the Potomac from Washington. This necessity, for an expedient, 

 proved that the transportation of ova by the dry method immediately 

 after they had been water-swollen was possible, and that it would an- 

 swer for long distances. To illustrate: some were kept on the trays in 

 good condition for seventeen hours iu the ordinary temperature of the 

 air, of 70° to 80° F., prevailing at that season of the year (July). When 

 the temperature of the air was up to 90° F. it was found that the ova 

 carried on trays and allowed to remain on them would tend to spoil 

 quickly, as bacteria and vibriones were distinguishable on all the spoiled 

 putrescent ova carefully examined under the microscope. It is there- 

 fore evident that in warm weather, iu transporting ova by the dry 

 method for long distances, it would be necessary to take certain precau- 

 tions to prevent the access of the germs of such putrefactive organisms 

 to the eggs. Essentially the same method of procedure recommended 

 to guard against the introduction of the spores of the saproleguious fun- 

 gus to the eggs would apply here. Such i^recautions, however, would 

 only be necessary where it was desired to retard the development for a 



