INVERTEBEATES OF LAKES GENEVA AND MENDOTA. 
485 
larvae of another species of Ohironomus and upon a variety of the smaller animal forms 
occurring among the weeds in the shallow water. The following are the details of the 
food of fourteen diseased perch and of nine healthy ones taken by hook or seine at the 
same time, the numbers being those from my laboratory catalogue of accessions. 
FOOD OF DISEASED PERCH. 
4929. The intestine of this specimen was empty, but the stomach was well filled 
with larvfe and pupie of the large red Ohironomus. 
4947. Full of large red Ohironomus larvm* 20 to 25 millimeters in length, and 
pupae of the same species 16 millimeters long. 
4948. A great quantity of food, consisting of the usual large red larv® and pupae 
of Ohironomus, 15 millimeters long, with some very fine dirt. 
4949. A moderate amount of the large Ohironomus larvae and pupae. 
4950. A rather small quantity of larvm and pupae of red Ohironomus, with some 
very fine dirt. 
4951. A moderate amount of the same material. 
4952. Red Ohironomus larvae and pupae, as usual, in very large quantity. A single 
crushed entomostracan of the order Oladocera. 
4953. The usual larvae and pupae of Ohironomus only. 
4954. As above, the larvm 20 millimeters in length. 
4955. A great quantity of food of the usual character and nothing else, the pupae 
predominating. 
4956 and 4957. Larvae and pupae of the red Ohironomus only. 
4958. This specimen furnished the only exception to the usual food of the dead 
perch taken. The stomach contained a moderate number of nymphs of Ephemera and 
ai few small white larvae and pupae of Ohironomus, the larvae 10 millimeters long. Al- 
though dead when taken, it is possible that this fish had not perished by disease. The 
objects which it had eaten are those found in relatively shallow water. 
4961. A rather smaill amount of food, not recently taken, the pupae and larvae of 
the red Ohironomus being chiefly in fragments. 
The contents of the alimentary canal of ten other specimens, not examined 
microscopically, was evidently of the same character. 
FOOD OF HEALTHY PERCH. 
4945. Ohiefly lairvae and pupae of Ohironomus, the former white, 10 millimeters 
long ; ailso two or three specimens of Allorchestes dentata^ and a long and slender case- 
worm with tube of sand. 
4946. A considerable number of small larvae and pupae of Ohironomus, white in 
color, several Allorchestes dentata, a single caseworm with sand tnbe, one specimen of 
Eurycercus lamellatus, and a single Oyclops. 
* The food of these larvie, determined by dissection, consisted of very tine mad, with a great 
quantity of minute vegetable debris, composed of various kinds of cellular structures. These were evi- 
dently in a state of decomposition, as shown by the vast numbers of bacilli and other bacteria everywhere 
among the contents. There was also occasionally a lilamentous alga resembling Oscillaria, and a few 
unicellular algm were noted. 
