302 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



velopment or " i>rematurity." We have had a good chance to test this 

 here, where the spriug-water is raised or lovyered in teiiiperatiire, accord- 

 ing to the weather, before it reaches the hatchery. Our hatching sea- 

 sons are long or short, according as the winter is severe or moderate. 

 Last year our eggs were laid in fully two weeks earlier and hatched 

 nearly a month later than this, yet the fish of this year are equal in vigor 

 and identical in appearance with those i^roduced last season. But there 

 is a very slight difference between the fry of the Northville hatchery, 

 and of the Detroit, Toledo, and Sandusky hatcheries ; the latter are a 

 little darker, a trifle less transparent. I used to think that this differ- 

 ence was due to diff'erence of hatchiugijeriods ; but since the fry of this 

 season that hatched earlier than ever before are identical with previous 

 hatchings, and since there is always the same difference between the 

 spring- water and lake-water fry, no matter whether the former are has- 

 tened or retarded, I am constrained to think that the difference, which, 

 however, is almost imperceptible, is due to the charactir rather than 

 the temperature of the water. Last year our tish were "kept back" 

 nearly as late as were those in hatcheries using lake-water. I know 

 that when we made a plant at the islands (Lake Erie) the tanks of the 

 Sandusky hatchery were full of whiteflsh minnows ready for distribu- 

 tion; and although there was not to exceed ten days in difference in 

 times of hatching, there was that same slight difference in color and 

 transparency. 



Our spring-water is clear and sparkling, free from mechanical impuri- 

 ties, but holding in solution sufficient calcic salts to make it quite hard. 

 The water used at the Sandusky and Toledo hatcheries is much softer, 

 but is quite roily at tiaies, and is never free from mechanical impurities. 

 When they were laying in eggs last fall the water was so bad that they 

 had to dispense with the wire gates through which the water discharges 

 from the jar, as they would get clogged with sediment in a short time 

 and overflow the jar. 



We have, at the hatchery here, brought forth the young of brook trout 

 in 80 days, and anon in 120 days; yet the former ate as readily, grew 

 as rapidly, suffered as little loss, and in fact were the equals in every 

 respect of the latter. The hatchery of the Michigan commission, for- 

 merly located at Pokagou, used spring-water for hatching their trout 

 eggs, without attem])tiug to cool it by extended exposure to the air. In 

 consequence of using this comparatively warm water their eggs frequent- 

 ly hatched in mid-winter — 1 presume in less than 80 days, but do not 

 not know positively. 'They had no trouble in rearing their fish. 



I am well satisfied that where we have had a chance to test this matter, 

 as with the young of fishes readily ad;ii)ted to being grown in confinement 

 in ponds or tanks, or "artificially" as brook trout, California trout, &c., 

 it makes no difference whatever, either as to the appearance of the fish, 

 or results in rearing, whether the eggs incubate a moderately short or 

 a very long time. There must, of course, be a limit to the brevity of the 



