287 



three-eighths of an inch wide, about twelve inches apart and one hundred feel 

 long, were formed west of Weaver's Point. 



In some instances the cracks seemed to be formed by an impact at right 

 angles to the field as if some subaqueous cyclpps had hurled a thunderbolt against 

 the frozen mass and sent fractures in all directions from this point as center. 



Off the Pickwick shore covering a large area the cracks were so numerous as 

 to suggest a fine intricate mosaic. This will to some extent explain the readiness 

 with which ice eight inches thick was removed by the wind and made to resembk' 

 slush in a few hours after nt begins to move. 



January 27, 1896, there occurred an unusual cracking of the ice, lasting all 

 day and far into the night. A constant bursting, crashing and booming pervaded 

 the whole lake. The noises suggested the crunching of heavy falling timbers and 

 the hoarse roar of distant cannonading. The day was clear, sun shining most of 

 the time, with temperature 26 to 34 degrees. The next day, with temperature 30 

 to 32, and cloudy, the lake was as silent as a cemetery. 



After several days' moderately high temperature, during the last week of 

 February the ice was well honeycombed. March 1st the temperature lowered tu 

 26, accompanied by a high north wind and snow. The drifting snow was driven 

 into the cells of the ice, making the whole field resemble a tine piece of oolite. 



The Plankton of Turkey Lake.* By Chancey .Juday. 



The data for this preliminary report were collected during July and August, 

 1896, at Indiana University Biological Station. To Dr. C. H. Eigenmann, Director 

 of the Biological Station, I am indebted for the plan of the net and for many 

 helpful suggestions. 



Hensen, who is the author of the term "plankton," applied this term to all 

 plants and animals which are found floating free and which are carried about 

 involuntarily by winds, waves, tides or currents. Haeckel extended the applica- 

 tion so as to include all swimming and floating organisms. At present, however, 

 those organisms that are not subject to the above-named physical forces are not 

 considered plankton, and they shall not be dealt with as such in this report. 



It has been demonstrated that a part of the plankton, the Crustacea, furnishes 

 nearly all the food of our most important fishes at a very critical period of their 

 lives, that is, while they are very young fry (Forbes, 1889). This makes plankton 

 a very important factor in the environment of these fishes. Its scarcity or abund- 

 ance and the relative amount of Crustacea will have much influence upon the 



'•'Contributions from the Zoological Laboratory of the Indinna University under the 

 direction of C. H. Eigenmann, No. ]9. 



