A LIMNOLOGICAL STUDY OF THE FINGER LAKES. 
595 
lakes. Two species, D. minutus and D. sicilis, were found in Cayuga and Seneca Lakes, 
but only the former species was present in the other lakes. In its vertical distribution, 
Diaptomus was found at all depths where the water contained a sufficient amount of 
dissolved oxygen. In Conesus and Otisco Lakes it did not occupy the bottom water, 
owing to the absence of oxygen, but the maximum number in both was obtained just 
above the low oxygen zone. The largest number in Conesus Lake, 43 individuals per 
liter, was found at 9 meters where the water contained 1.5 cc. of oxygen, but the number 
fell below i per liter at 10 meters where the water contained only o.ii cc. of free oxygen 
per liter. In Otisco Lake the largest number was found in the 9-12 meter stratum 
where the oxygen decreased from 5.8 cc. at 9 meters to 0.34 cc. at 12 meters. 
The largest catch of Diaptomus was obtained at the surface of Canadice Lake, 
48 individuals per liter. This was a rather unusual distribution, since this form usually 
avoids a few meters of the upper water in the daytime. The second largest catch was 
that on Conesus Lake, noted above. In Seneca Lake the maximum number, 20 per 
liter, was found at 50 meters. In both Seneca and Cayuga Lakes, Diaptomus showed 
a diurnal movement of about 10 meters. 
Representatives of the genus Cyclops were found in all of the lakes. In Seneca and 
Cayuga Lakes this form was most abundant in the upper 50 meters, although it extended 
to the bottom. In some lakes, however, it was confined entirely to the upper water. 
In Canandaigua Lake it was not found below 15 meters; in Skaneateles Lake, not below 
the 20-30-meter stratum; and in Owasco Lake, not below the 10-15- meter layer. This 
was a rather unusual distribution, since in general Cyclops seems to experience no 
difficulty in occupying much deeper water than is found in these lakes. Their absence 
from the lower water was not due to a scarcity of dissolved oxygen, because there was an 
abundance of it in the bottom water of these lakes, in fact almost or quite as much as 
at the surface. 
In Keuka Lake Cyclops was most abundant in the upper 10 meters, but in Canadice 
and Hemlock Lakes it was distributed rather uniformly from surface to bottom. In 
Conesus Lake its distribution was similar to that which has been found frequently 
in some of the Wisconsin lakes, viz, a fairly uniform distribution in the epilimnion 
with a maximum number in the thermocline, where there is a rapid decrease of the 
oxygen. The maximum number, 62 per liter, was found at 10 meters, where the dis- 
solved oxygen amounted to only o.ii cc. per liter. But in Otisco Lake, where there 
was also a rapid decrease of dissolved oxygen in the thermocline, no such phenomenon 
was found, there being a fairly uniform distribution in the epilimnion with only a small 
number below this stratum. 
Limnocalanus in small numbers was found in five lakes — Cayuga, Seneca, Canan- 
daigua, Skaneateles, and Owasco. It was confined to the hypolimnion, or lower stratum, 
of all of these lakes. A very few specimens of Epischura were obtained in Keuka and 
Owasco Lakes. 
The copepod nauplii showed great diversity in their vertical distribution. They 
were found at all depths in the majority of the lakes, but they were more abundant 
