77 



nated January 1, 1890, filled the lake, and the water slowly decreased until 

 November, when the few shallow pools that remained were frozen solid. 

 Water again entered the lake January 6, 1897, and the last pool was dried up^ 

 about September 1 the same year. Toward the last of February, 1898, rising 

 waters again poured into the lake, and owing to the high water of the past 

 spring continued to occupy it and the adjacent territory until the middle of 

 July. Since that time the depth of the water has decreased rapidly and by the 

 rniddle of September the lake was reduced to a few large pools. During the first 

 half of 1896 monthly collections were made, and since that date the interval 

 has been reduced to a fortnight. 



During the past year a drainage district has been organized in the territory 

 including and adjacent to Phelps lake. The object of this organization is 

 the reclamation of the fertile bottom south of Spoon river. A large dike is 

 being built along the north limit of the district, reaching the river a short 

 distance above the north end of Phelps lake. From this point it passes 

 southward along the river bank for several miles to a point some distance 

 below the mouth of Phelps lake slough, and then turns westward to the 

 west bluff. The drainage of the enclosed area will be accomplished 

 by several large ditches leading to the southeast, where pumping works 

 are planned to insure the removal of the water when the surrounding 

 country is flooded. Owing to the drainage of this lake our opei-a- 

 tions in this locality must cease with the present season, which leaves us in 

 possession of quantitative collections extending through three years, in each 

 of which the water entered in the winter or spring overflow, and was slowly 

 removed by evaporation and seepage throughout the summer months, the 

 catastrophe culminating in the late fall. We have thus in our possession a 

 basis for a tolerably complete record of the seasonal fluctuations and changes 

 in the fauna and flora incident to the drying up of this ephemeral bodj' of 

 water. 



Since September, 1896, collections have been made in Spoon river at inter- 

 vals of a month or less, and during this time a number of qualitative towings 

 have been taken for us by Mr. W. R. Deverman, of Topeka, ill., from the 

 waters of Quiver creek. We have thus a good series of collections from 

 tributary streams of the river for a comparison with those of the river itself. 



A plankton station was established in September, 1895, in Flag lake, a 

 large marsh between Thompson's lake and the Illinois river. Collections 

 have been made here from that time at intervals of a month or less and were 

 continued in 1897 until July. Owing to the abundance of vegetation in Flag 

 lake this station was extremely difficult of access during the summer 

 months, and owing to the abundance of flocculent debris of vegetation it was 

 at all times difficult to secure a satisfactory quantitative collection from this 

 body of water. As it was necessary to reduce the amount of field work, it 

 seemed best for these reasons to drop this station permanently from the list 

 of places subject to regular visitation. During the summer of 1898 plankton 

 collections have been made from time to time at the mouth of Flag lake 

 slough in the hope of finding here Trochospharn, as in former years. None, 

 however, could be found in this locality or, indeed, in any other in our field 

 of operations during the past summer. 



As a rule the collections made at the plankton stations above enumerated 

 included a vertical one, one from the surface, and one from the bottom 

 water, all made with a pump and a net of No. 20 silk bolting cloth. In addi- 

 tion to these a catch from a liter of water from a vertical sample at each sta- 

 tion was made with filter paper, and from five liters with the Berkefeld filter, 

 the first method of filtration being introduced in September, 1896, and the 

 secoi^d in November, 1897. The total number of bottles in the regular series 

 for the years 1897 and 1898, each representing a different catch, is 1,075. 



The collections above mentioned belong to the chronolgical series whose 

 purpose is to afford a quantitative and (jualitative representation of the 

 changes through which the life in the water of the streams and the lakes ex- 

 amined passes during the course of a term of years. In addition to this series- 

 a considerable number of othtr catches have been made with a view to secur- 

 ing data upon certain allied and important phases of the plankton work. 



