MILNER FISHERIES OF THE GREAT LAKES. 57 



difference in the rapidity with which the umbilical sac disappeared, as the 

 young fish I had carried home were in the same stage of development, 

 April 14, as when I had visited Clarkstou i)reviously. ISTow, May 1, the 

 fish in Mr. Clark's troughs still retained considerable of the sac, while 

 on the 28th of April the young fish in the jar had lost it entirel}'. The 

 jar had been kept in a moderately warm room, with a temperature of 

 about G5°, while the water in the troughs at Clarkstou flowed from a 

 pond that had been covered with ice until within a few days previous. 



(22 g.) Food of emhryonic white-fish. — The young fish reached Wauke- 

 gan in safety, and were placed in five quart glass jars, and an experi- 

 ment begun in attempting to supply them with suitable food. A num- 

 bered label was pasted on each jar, so as to keep them distinct. 



Knowing that the larger white-fish fed largely on crustaceans, an at- 

 tempt to feed them on food of this character was thought worth a trial. 

 A few craw-fish were procured and pounded to a paste, and small por- 

 tions put into jar No. 1; the young fish ate it readily. They were fed 

 at night, and the next morning every oue of them was found to be 

 dead. Jar I>ro. 2 was supplied with bread-crumbs, and the fish were 

 seen to take small particles in their mouths; they did not die so sud- 

 denly. Jar Xo. 3 was supplied with sweet cream, but no evidence was 

 afforded that the occupants fed upon it. A quantity of rain-water was 

 exposed to the rays of the sun for the purpose of generating minute 

 forms of life, and a teaspoonful was poured into jar Xo. 4, morning and 

 evening, in hopes that their proper food was of this character. In jar 

 No. 5 a variety of food was provided, dry fresh beef, mi)k, boiled 

 potato, and bread. The crumbs of bread and the scrapings from the 

 beef were all that the fish were seen to take into their mouths. They 

 died, one after another, very rapidlj', and in a few days all were dead. 



There were other things unfavorable to them, in these experiments, be- 

 sides the lackof their natural nourishment. To conduct these experiments 

 favorably, they should be placed in a large vessel, and a stiNeam of fresh 

 water should be supplied constantly so that the water should continue 

 pure and the production of confer va3 be avoided. This difficulty of pro- 

 curing a suitable food for the young white-fish has been the experience 

 of the few fish-culturists who have hatched them. 



A set of specimens representing young fish from the Detroit Eiver, 

 from the troughs at Clarkstou, and from the jars, were preserved in 

 alcohol and submitted to Mr. S. A. Briggs, editor of the Lens, Chicago. 



A letter from Mr. Briggs containeJ the following: 



" Chicago, May 28, 1872. 



''My Deaii Sir: The four vials containing C. albus came duly to 

 hand, and have, with the alcohol and water in which the specimens were 

 preserved, been carefully examined. 



'' The intestines of specimens No. 77 and 78, from Clarkstou, were en- 

 tirely destitute of organic matter recognizable under a power of 400 

 linear, which ouglit to be ample for the purpose. 



