448 
Birge—The Crustacea of the Plankton. 
Table J.— Chydorus .— Average , maximum , and minimum numbers. 
Percentile vertical distribution. 
Av. 
Max. 
Min. 
Per cent, in each 3 m. level. 
0-3. 
3-6. 
6-9. 
9-12. 
12-15. 
15-18. 
1894. 
Sept. 16-30.. 
278.9 
440.7 
96.6 
55.0 
26.9 
10.6 
5.6 
2.0 
0.0 
Oct. 1-15.... 
193.3 
251.2 
92.8 
12.3 
13.3 
16.4 
21.6 
21.6 
14.8 
Oct. 16-31... 
202.0 
304.6 
82.0 
14.2 
17.8 
18.0 
18.7 
19.9 
11.3 
Nov. 1-15.... 
97.9 
261.3 
13.3 
7.3 
15.5 
18.6 
28.4 
19.3 
10.8 
Dec. 1-15.... 
9.5 
15.9 
3.8 
16.7 
20.6 
13.3 
16.7 
18.7 
14.0 
1895. 
June 1-15 ... 
36.7 
92.8 
11.1 
41.9 
24.9 
13,0 
9.4 
5.0 
5.6 
June 16-30 .. 
21.9 
45.7 
6.9 
83.1 
13.4 
2.4 
1.1 
0.0 
July 1-15.... 
156,8 
271.5 
13.3 
61.1 
25.3 
11.0 
2.2 
0.4 
0.0 
July 16-31... 
163.4 
283.6 
89.0 
42.8 
35.2 
20.3 
1.2 
0.2 
0.2 
Aug. 1-15 ... 
78.6 
157.7 
16.8 
43.2 
30.4 
18.4 
7.3 
0.5 
0.1 
Aug. 16-31 .. 
18.7 
48.7 
5.0 
32.7 
33 3 
21.8 
11.2 
1.1 
0.0 
Sept. 1-15... 
15.6 
39.4 
8.9 
45.5 
23.6 
22.8 
4.8 
3.4 
0.0 
Sept. 16-30.. 
Scatte 
ring 
only. 
Oct. 1-15.... 
8.6 
14.3 
5.0 
17.6 
17.6 
6.6 
12.5 
14.7 
30.9 
Oct. 16-31... 
8.1 
12.0 
3.8 
46.8 
14.1 
7.8 
23.5 
7.8 
0.0 
Nov. 1-15_ 
25.9 
46.4 
10.8 
11.4 
15.3 
14.3 
24.3 
21.3 
13.4 
Nov. 16-30... 
19.7 
29.8 
13.9 
9.2 
18.8 
24.0 
21.6 
]6.1 
10.3 
Dec. 1-15.... 
15.9 
19.7 
12.0 
26 0 
6.6 
18.2 
10.5 
16 8 
22.0 
Dec. 16-31... 
20.9 
36.8 
8.9 
23.0 
18.6 
11.8 
22.6 
17.6 
6.3 
1896. 
May 1-15_ 
28.0 
48.3 
19.0 
15.9 
23.4 
23.8 
16.2 
8.9 
11.8 
May 16-31... 
30.8 
68.6 
13.3 
34.0 
23.6 
15.9 
19.9 
4.3 
2.3 
June 1-15_ 
87.6 
279.8 
4.4 
77.6 
15.8 
4.7 
1.0 
0.4 
0.3 
June 16-30.. 
230.8 
346.0 
145.6 
65.0 
24.4 
7.0 
2.6 
0.5 
0.3 
July 1-15_ 
382.0 
661.4 
169.8 
57.0 
33.6 
6.9 
2.0 
0.3 
0.0 
July 16-31... 
245.1 
465.5 
129.1 
43.2 
34.1 
20.0 
2.7 
0.2 
0.0 
Aug. 1-15_ 
406.5 
54.8 
32.0 
10.4 
2.2 
0.5 
0.0 
Aug. 16-31 .. 
426.0 
32.4 
36.2 
21.0 
8.5 
1.7 
0.1 
Sept. 1-15 .. 
748.6 
34.9 
26.7 
17.0 
15.2 
5.6 
0.7 
Sept. 16-30.. 
263.0 
25.0 
14.8 
14.9 
12.2 
18.1 
14.9 
Oct. 1-15.... 
423.7 
10.3 
15.0 
25.8 
21.0 
14.5 
13.4 
Oct. 16-31... 
191 9 
16.9 
18.1 
17.1 
12.8 
16.6 
18.4 
Nov. 1-15 ... 
62.7 
18.7 
22.4 
13.0 
13.4 
12.7 
19.8 
Nov. 16-30 .. 
69.3 
21.3 
12.0 
26.7 
17.3 
10 6 
12.1 
Dec. 1-15_ 
38.2 
15.0 
16.2 
13.4 
19.1 
16.2 
20.1 
Dec. 16-31... 
28.1 
12.8 
25.0 
15.0 
17.6 
19.6 
10.0 
