V2 



an ineh-and-a-lialf mesh, hung to fish eight feet ; a forty-yard 

 minnow seine of one-fourth-inch mesh, hung to fish five feet ; 

 a , thirty-foot minnow seine, hung to fish four feet ; a Baird seine 

 of the same dimensions ; and a trammel net thirty yards in 

 length and five feet in depth. The additions to the equipment 

 consist of two set nets, one of three-fourths-inch mesh and 

 eighteen-inch hoops, the other of an ineh-and-a-half mesh and 

 four-foot hoops. Thirteen fish traps of quarter-inch galvanized 

 wire netting were constructed especially for the work in deep 

 water and in places where a minnow seine could not be used. 

 They consist of a cylinder of netting ten inches in diameter, 

 one end of which is closed by a circle of wood and the other by 

 two successive funnels sloping inward, each with an opening 

 tln-ee inches in diameter. For the capture of the smallest fish 

 the nets are covered with fine wire cloth, and their efficiency is 

 also increased by the use of wings of the same material or of 

 minnow netting. 



The plankton operations of the last two years have been 

 carried on with increased regularity and greater attention to the 

 correction of possible sources of error. The number of stations 

 subject to regular examination at the beginning of the period 

 covered by this report was seven; viz., the Illinois River two 

 and a half miles above Havana, Quiver Lake, Dogfish Lake, 

 Thompson's Lake, Flag Lake, Phelps Lake, and Spoon Eiver, 

 the latter having been added to the list in August, 1896. (See 

 Plate I.) The Illinois River station was visited at intervals of 

 one month until July, 1896, in which month a number of ex- 

 aminations were made at frequent intervals during a remark- 

 able development of a filamentous diatom, Mrlosini, in the 

 plankton, and in correlation with gas analyses conducted by 

 Professor Palmer. Weekly collections upon Tuesdays were 

 begun August 3, 1896, and have since been maintaineil except 

 when the condition of the ice or sickness necessitated a slight 

 shifting of the day of collection. 



The station in Quiver Lake was visited duiiiig intervals of 

 one month during the first half of 1897, but during the latter 

 part of July and the months of August and Septemlior the inter- 

 val was reduced to a week. In October fortnightly visits were 

 commenced, and have since l)een maintained. In the summer 



