General Distribution of the Crustacea. 
439 
the Crustacea could be traced to these varying conditions of the 
weather. It is worth noticing that the number of Crustacea 
obtained was not to any notable extent affected by the direction 
of the wind. Since our buoy was placed about -J of the distance 
across the lake, it might reasonably have been expected that 
the pelagic Crustacea would be decreased in number by a breeze 
blowing from the nearer shore, and possibly somewhat increased 
by a wind from the farther shore. No such effect, however, was 
observable and indeed the number of Crustacea obtained in the 
last period, when the wind was from the more distant shore, 
was smaller in all species than the number obtained in the pre¬ 
ceding series, when the wind was from the nearer shore. 
GENERAL DISTRIBUTION OF THE CRUSTACEA. 
Altogether 59 sets of observations were counted, and are 
made use of in determining the average of the distribution ot 
Crustacea for the month. The number of observations varies 
somewhat in the different levels. Forty-nine observations only are 
recorded for the lowest level, 15-18 m., for reasons indicated 
above. In each of the upper levels, except the upper, from one 
to three observations were lost by various accidents. In one or 
two cases the dredge did not open or close properly, thus vitiat¬ 
ing the observation. In one or two cases the contents of the 
dredge were partially lost, thus making it impossible to count 
them. However, the general uniformity of observations is such 
that no noteworthy change would be made in the results if all 
the sets of observations had been perfect. In the last three 
periods observations were taken'at intervals of three hours dur¬ 
ing the day and night. The times selected were midnight, 3 
a. m., 6 a. m., etc. The observations taken at 9 p. m., mid¬ 
night, and 3 a. m. are reckoned as belonging to the night. 
Those at the other hours are reckoned as belonging to the day. 
In July, of course, the hours of 6 a. m. and 6 p. m. are fully 
within the daylight hours. Had there been any diurnal move¬ 
ment of the Crustacea these observations would have been 
treated by themselves, but since the day observations do not 
differ in any marked way from those made at night, the 6 a. m. 
and 6 p. m. series are included and averaged with those of the 
