1894.] Zoology. 807 
ZOOLOGY. 
On the Vertical Distribution of Pelagic Crustacea in 
Green Lake, Wisconsin.—Green Lake is the deepest body of 
water in the State of Wisconsin, having a maximum depth of about 60 
meters. Because of its great depth it has not only the litoral and pela- 
gic faunz of the shallower bodies of water, but also the true abyssal 
fauna which is characteristic of the deeper lakes. In fact, the crusta- 
cean fauna of Green Lake is almost identical with that of the great 
lakes. 
In the deeper waters of Green Lake are found fifteen species of crus- 
tacea. Of these, twelve may be fairly considered as belonging pecu- 
* liarly to the deep water fauna. Most of these can be captured in very 
large numbers at night by means of the skimming net. During the 
day, very few are found at the surface, some few never come to the 
surface, and are only obtained by dredging in the deep water. 
Of course, an open dredge, dropped from the surface to the bottom 
and then hauled up, will collect from all depths. After a little experi- 
ence, the collector has no difficulty in distinguishing between pelagic 
and abyssal species, and can even draw inferences, with a reasonable 
degree of accuracy, in regard to the general vertical distribution of 
species. So far as I know, however, very little exact work has 
done to determine the vertical limits of the various species. By means: 
of dredges which could be closed at any required depth, it has been. 
found that in the deep sea there is a surface fauna and a deepwater 
fauna, but that the immediate intermediate region is barren of animal 
life. According to Agassiz, the surface fauna extends to the depth of 
200 fathoms, and the bottom fauna is limited to about 60 fathoms. 
Is there a similar condition in the waters of our lakes? With a view 
to answering this question, I made some preliminary collections in the 
summer of 1893. 
I used, for the collections, a vertical dredge, so constructed that it 
could be closed at any desired depth. The collections upon which this 
paper is based were made in the latter part of August, at all hours be- 
tween five o’clock in the morning and nine o’clock at night. Each 
series included collections for every five meters in depth. Of course, 
until a much larger number of collections is made, and at different sea- 
sons of the year, no final conclusions can be drawn. But the results 
