104 The First Food of the Common White -Fish. 



on these fourteen fishes, we may say that eight of them ate a sin- 

 gle Cyclops each, that one took two, and another three of the 

 same, that one took a single Canthocamptus, that two specimens 

 captured two each of this genus, and that finally, a single fish ate 

 Cyclops and Canthocamptus both. The final conclusion was a 

 highly probable inference that the smallest Entomostraca occur- 

 ring in the lake would prove to be the natural first food of the 

 species. 



In order to test this conclusion with precision, I arranged a sim- 

 ilar experiment on a larger scale and under more natural condi- 

 ditions. Through the generosity of the Exposition company, of 

 Chicago, I was allowed the use of one of the large aquarium tanks 

 in the exposition building on the lake shore, and by the repeated 

 kindness of Mr. Clarke, of Northville, Michigan, I was furnished 

 with a much larger number of living white-fish. Five thousand 

 fry were shipped to me in a can of water, but through unfortunate 

 delays in changing cars at intermediate points, about two-thirds 

 of these were dead when they reached my hands. Those living 

 were immediately transferred to the tank, through which the 

 water, taken from the city pipes, had already been allowed to run 

 for several hours. As this water is derived from Lake Michigan 

 at a distance of two miles from the shore, and had at this time the 

 exact temperature of the open lake, the conditions for experiment 

 were as favorable as artificial arrancrements could well be made. 



Sending a man with a towing net out upon the lake with a 

 boat, or upon the remotest breakwaters, immense numbers of all 

 organic objects in the water were easily obtained. After enclosing 

 the exit of the tank with a fine wire screen, to prevent the escape 

 of objects placed in it, we poured these collections of all descrip- 

 tions indiscriminately into the water from day to day, thus keep- 

 ing the fishes profusely supplied with all the various kinds of food 

 which could possibly be accessible to them in their native haunts. 

 From this tank one hundred fishes were taken daily and placed in 

 alcohol for dissection and microscopic study, to determine pre- 

 cisely the objects preferred by them for food. These were ex- 

 amined at a later date, and all contents of the intestines were 

 mounted entire as microscopic slides, and pemanently preserved. 

 A careful study, was of course made of the organisms of the lake, 

 as shown by the product of the towing net, and when the experi- 



