Juday—Quantitative Studies of Fauna in Lake Mendota. 487 
Table 4. Numerical results obtained for Pisidium at the five deep¬ 
water stations and at station I. The figures given for maximum, mini¬ 
mum, and mean indicate the number of individuals per square meter of 
bottom. 
Station 
Number 
of 
Samples 
Number of Individuals per Square 
Meter 
Maximum 
Minimum 
Mean 
Station II ... 
73 
1,510 
42 
690 
Maple Bluff . 
32 
1,200 
42 
360 
Center ... 
44 
1,540 
63 
660 
North of Second Point. —.. 
32 
1,140 
21 
426 
West Bay ... 
35 
1,076 
42 
450 
Station I .... 
52 
1,690 
105 
570 
Table 5. This table shows (1) the average dry weight of the different 
sizes of Pisidium in milligrams, (2) the percentage of ash in the body 
part, (3) the percentage of the total weight constituted by the body of the 
animal, (4) the percentage of the total weight consisting of shell, and 
(5) the percentage of organic matter in the shell. 
Size 
Average 
Dry Weight 
of Body 
Part, 
Milligrams 
Percentage 
of Ash 
in Body 
Part 
Percentage 
of Total 
Weight 
Composed 
of Body 
Part 
Percentage 
of Total 
Weight 
Consisting 
of Shell 
Percentage 
of Organic 
Matter 
in Shell 
Large . 
5.0 
2.18 
17-21 
79-83 
6.6 
Medium . 
1.4 
2.55 
17.4 
82.6 
5.4 
Small . 
0.4 
10.40 
21.0 
79.0 
4.4 
Table 6. The average number of larvae of Chironomus tentans per 
square meter of bottom at the regular stations, and the average number | 
of the different sizes in the samples in which they were counted sepa¬ 
rately. 
Station 
Number 
of 
Samples 
Average 
No. per 
sq. m., 
All Sizes 
Number 
of 
Samples 
Average Number per Square 
Meter, Different Sizes 
Large 
Medium 
Small 
Station II .. 
92 
549 
66 
79 
176 
434 
Maple Bluff . 
39 
885 
37 
121 
351 
424 
Center . 
54 
566 
45 
89 
176 
370 
North of Second Point. 
39 
472 
37 
81 
157 
197 
West Bay ... 
39 
566 
34 
65 
182 
324 
Station I . 
64 
872 
54 
112 
324 
574 
