Marsh-—Limnetic Crustacea of Green Lake. 
217 
GENERAL CONCLUSIONS IN REGARD TO VERTICAL DISTRIBUTION. 
I had supposed that there was a general movement of the 
whole body of erustacea in such vertical migrations as existed. 
It is evident that this is not the case, for the different kinds 
have their individual peculiarities of distribution. 
In the case of Diaptomus there is little or no vertical migra¬ 
tion from any cause. 
Epischura avoids bright light, and has a preference for warm 
water, and shows both seasonal and diurnal migrations. 
Limnocalanus is repelled by bright light and by a high tem¬ 
perature, hence its diurnal migration is more pronounced in 
cold weather. 
Cyclops brevispinosus occurs most abundantly between five and 
twenty meters in depth. I have no evidence in regard to its 
diurnal migrations. 
Cyclops fluviatilis has no diurnal migration, but in its seasonal 
distribution shows a preference for the warmer water. 
Leptodora is a surface form. I have no conclusive evidence 
in regard to its diurnal migrations. 
Daphnia kahlbergienses apparently moves towards the surface 
at night. 
There is no appreciable difference in the seasonal distribution 
of Bosmina. There is a distinct diurnal migration due to its 
attraction to light. 
Daphnella has a diurnal migration due to the fact that it is 
repelled by light. 
I cannot make out from my collections that the winds have 
any effect on the vertical distribution of entomostraca. The dis¬ 
tribution when the surface is roughened by waves seems to be 
practically the same as when it is smooth. Neither is there 
any marked difference between dark and moonlight nights. 
It must be remembered, however, that all my collections were 
at five meter intervals, and that there may be migrations within 
these limits of which I have no indication. I know for instance 
from surface tows that the immediate surface is almost entirely 
devoid of entomostraca in the day time, but is populated in 
enormous numbers in the night. There is evidently a very 
