The Distribution in the Upper Meter. 
407 
THE DISTRIBUTION IN THE UPPER METER, AND THE DIURNAL MOVE¬ 
MENT. 
Figures 32, 33. 
The observations recorded in my former paper showed uni¬ 
formly that there was no general diurnal movement of the Crus¬ 
tacea and no movement at all which couid be detected by the 
use of three-meter intervals. This conclusion has been con¬ 
firmed by all of the observations which I have since made. 
During 1895 and 1896 considerable attention was paid to the 
distributiou of the Crustacea in the upper meter, with the de¬ 
sign to determining whether or not there was a diurnal move¬ 
ment of the limnetic forms within narrower limits than three 
meters. A large number of observations were made in 1896 in 
order to determine the relative number of Crustacea in the upper 
meter and the remainder of the 3 m. level. These observations 
were begun early in August and continued until the last of No¬ 
vember; twenty sets of observations being made in all. In 
some cases the Crustacea were taken meter by meter and the 
numbers compared. In other cases the Crustacea of the upper 
meter were caught and their numbers compared with those ob¬ 
tained from the entire depth. A single illustration of the 
former method is given; partly in order to show the results, 
partly also to illustrate the amount of agreement and difference 
between the three catches of one meter each and that made 
through the entire distance of three meters. 
Table XXXVI. — Number of Crustacea caught August 24, 1895. 6 P. M. 
Depth, meters. 
Diapto- 
mus. 
Cyclops. 
D. hyalina. 
D. retro- 
curva. 
Diaphan- 
osoma. 
Chydorus. 
0-1. 
700 
360 
2,120 
280 
140 
100 
1-2. 
340 
360 
2,060 
200 
140 
120 
2-3. 
460 
370 
1,150 
160 
50 
50 
Total... 
1,500 
1,090 
5,330 
640 
330 
270 
0-3.. 
1,780 
1,050 
4,250 
475 
350 
375 
As would naturally be expected, the ratio between the c i 
tacea of the upper meter and those of the entire level varies 
