a 
2. It is doubtful if the various species of ciscoes show any preference among 
the entomostraca as food material. They doubtless take whatever forms occur 
in the waters they happen to inhabit. 
3. In the great majority of alimentary tracts examined, Daphnia formed the 
great bulk of the contents, while other forms were represented by scattered 
individuals. In many cases Daphnia alone were present. This was particularly 
true of the jumbo and the Lake Ontario ciscoes. It appears, therefore, that 
Daphnia are very much the most important of the entomostraca as food organisms. 
Daphnia longispina occurred in all the material examined, as variety hyalina 
galeata. Daphnia ephippia were abundant in October in Lake Ontario and in 
November in Lake Erie. Occasional ephippia with three eggs were noted. 
4. Of the. Copepods Diaptomus sicilis and Limnocalanus macrurus were 
perhaps the most abundant forms occurring in the digestive tracts, although 
Epischura lacustris occurred frequently and occasionally in considerable numbers. 
Very often the oil globules of these forms gave the contents a bright red colour. 
5. In the eastern end of Lake Erie one of the most important food organisms | 
was Mysis relicta. As far as we are aware this is the first record of the occurrence 
of this form in Lake Erie. Its presence indicates at least an approach of con- 
ditions in the eastern end of this lake to conditions in the other Great Lakes. 
6. Three individuals were found to have eaten small fish. In each case 
digestion had proceeded too far to allow of identification. All three ciscoes 
were taken in the eastern end of the lake, two were longjaws (L. prognathus) 
and the third, while not definitely identified, was probably -also a longjaw. A 
fisherman near Point Pelee has stated that one winter he found that some 
ciscoes which he took through the ice, had eaten “minnows.” 
7. As is shown in the table for the longjaws (L. prognathus) these fish in 
June, 1919, had fed practically entirely upon Ephemeridae (Ephemera simulans), 
both adults and subimagoes. The importance of these insects as fish food is 
thus further demonstrated. Moreover, there is no doubt that the transforma- 
tion of the nymphs to the subimaginal stage takes place at the surface of the 
water, as occurs in the closely related genus Hexagenia (Needham, 1920).* 
This means that the subimagoes, as well as the imagoes, were taken at the 
surface of the water by the ciscoes. The projecting lower jaw of these forms is 
well suited to such surface feeding. 
8. The following table, compiled from the food tables, shows the distribution 
of the food organisms in the lake. 
The outstanding points in the table are: 
(a) The absence of Mysts relicta from the western portion and the absence of 
Daphnia pulex and D. retrocurva from the eastern portion. Further investiga- 
tion, however, may show the presence of these species throughout the lake. 
(b) Although only 43 gill net fish were examined, and the list of forms is, 
therefore, incomplete, yet the results are an indication of what would be expected 
in any large body of water, namely, that the shore waters contain a greater 
number of species of food organisms than the more open waters. The gill net 
*Needham, James G. 1920. Burrowing Mayflies of our Larger Lakes and Streams. 
Bull. U.S. Bur. Fish., Vol. XXXVI, 1917-18. 
90 
