20 



niological stiulies, inolluscan collections and determinations, fresh-water 

 worms, studies of Protozoa and Rotifera, chemical determinations, reports 

 and publications, and the summer opening of the Station. 



PLANKTON' OPKKATIONS. 



The minute plant and animal life suspended in the waters of a river sj-steni, 

 moving downwards with its current and washed to and fro by its waves, com- 

 poses what is known to the modern biologist as the plankton of its waters. The 

 Station operations in this tield were primarilj' directed to a study of the amount 

 of this plankton in the various locations selected, its seasonal and other 

 periodic changes, its local and vertical distribution, its composition as to the 

 species represented, and its relation in the general system of aquatic life. 

 Our field of operations is a unique one, as yet practically untouched by the 

 scientific investigator, in so far as it is limited to a river system and its de- 

 pendent waters. 



The plankton substations in 1894 and 1895 were five in number, one in the 

 river, a short distance above the foot of Quiver Lake, another in Qviiver Lake 

 itself, a third in Dogfish Lake, a fourth in Thompson's Lake, and a fifth in 

 Flag Lake, between Thompson's Lake and the river. To these were added in 

 189G a substation at Phelps Lake, from which, indeed, a single quantitative 

 collection had been made in 1894, and another in Spoon River a short dis- 

 tance above its mouth. From these various substations a thousand quantita- 

 tive collections have been made since the Station opened, those from April. 

 1894, to June 30, 1895, by Professor Frank Smith or under his immediate 

 direction and those subsequent to that time by Dr. C. A. Kofoid. All these 

 tows have of course been carefully preserved by methods such as to permit 

 their quantitative comparison and about three fourths of them have been 

 quantitatively determined by Dr. Kofoid by methods of precise measure- 

 ment. A considerable beginning has also been made in the enumeration of 

 their contents by counting under the microscope. 



Various modifications of plankton methods, elaborate tests of the apparatus 

 used and of the methods of discussion current, and other items of improve- 

 ment in the equipment and in the methods of planktologj- will be reported by 

 Dr. Kofoid in a paper on this department of our work now nearly ready for 

 the press. For certain general conclusions of considerable interest and of at 

 least provisional value reference may be made to the same paper. 



COLLECTIONS ACCUMULATED. 



The total number of lots of specimens collected since the opening of the 

 Station amounts to (),028, besides 5,500 pinned insects. Of the former, 434 

 lots contain materials for a study of the food of animals, 300 of them being 

 the contents of the stomachs of fishes; 270 are specimens of vertebrates; 

 3,500 are preserved collections of invertebrate animals; 1,823 are towing-net 

 collections; and 543 were collections of Rotifera and Protozoa, most of which 

 were studied alive because incapable of satisfactory preservation. The entire 



