146 PLANKTON OF WISCONSIN LAKES 



averages for the other three lakes, but the percentage of ether extract 

 is a little larger than the average of Lake Waubesa. The percentage of 

 the pentosans falls below the averages for the net material from Monona 

 and Waubesa, but it is larger than the average of Mendota; the per- 

 centage of crude fiber, on the other hand, is larger than the averages 

 of Monona and Waubesa, but smaller than the mean of Mendota. To- 

 gether the crude protein, ether extract, and crude fiber constitute 53.36 

 per cent of the organic matter in the net catch from Lake Kegonsa, 

 leaving 46.64 per cent as nitrogen free extract. The pentosans make 

 up 4.36 per cent of the nitrogen free extract which leaves 42.28 

 per cent of the dry organic matter as undetermined carbohydrate 

 material. 



The Nannoplankton 



Lake Mendota. The second part of table 25 gives a general summary 

 of the nannoplankton for the three lakes from which such material was 

 secured. A summary of the net samples corresponding to the nanno- 

 plankton catches is given also in order to show figures that are directly 

 comparable for the two series of samples. 



The dry organic matter of the nannoplankton of Lake Mendota varied 

 in amount from a minimum of 795 milligrams to a maximum of 3,151 

 milligrams per cubic meter of water. (Table 17.) The average amount 

 for the entire series of nannoplankton catches is 1,630 milligrams per 

 cubic meter. (Table 25.) Nitrogen constituted 6.84 per cent of the 

 mean quantity of organic matter (equivalent to 42.75 per cent of crude 

 protein), ether extract 6.55 per cent, the pentosans 4.82 per cent, and 

 the crude fiber 5.19 per cent. The percentages of nitrogen, ether ex- 

 tract, and crude fiber are smaller than those of the corresponding sam- 

 ples of net plankton, but the percentage of pentosans is larger. The 

 crude protein, ether extract and crude fiber make up 54.49 per cent 

 of the organic matter in the nannoplankton of Lake Mendota and the 

 remainder consists of the carbohydrates which constitute the nitrogen 

 free extract. Of the latter, the pentosans make up 4.82 per cent. 



In the deep water of Lake Mendota the organic matter of the nanno- 

 plankton ranged from 175 kilograms to 694 kilograms per hectare (155 

 pounds to 619 pounds per acre), while the average quantity for the en- 

 tire series of nannoplankton samples was 359 kilograms per hectare, or a 

 little more than 320 pounds per acre. When the entire body of water is 

 taken into account the mean quantity of dry organic matter becomes 198 

 kilograms per hectare of surface, or about 177 pounds per acre. 



Lake Monona. The 21 samples of nannoplankton from Lake Monona 

 gave an average of 2,350 milligrams of dry organic matter per cubic 

 meter of water, with a minimum of 666 milligrams and a maximum of 

 5,696 milligrams. (Tables 25 and 29.) Of the mean quantity of 



