INVERTEBRATES OF LAKES GENEVA AND MENDOTA. 
481 
year; but a haul in only 20 feet of water on the rocky reef above mentioned gave the 
common deep-water forms, Pisidium adamsi and the red CMrononius,* with an occa- 
sional Corethra larva also. 
The shallow-water dredgings of 1885 were much more fruitful than those of 1884, 
giving many times the number of individuals, and especially a greater number of case- 
worms and small crustaceans {Allorchestes). 
A cursory examination of a haul of the dredge made on the sandy shallow, likewise 
dredged in 1884, showed an abundance of Allorchestes dentata and small white Chiro- 
nonius larvrn, a multitude of case-worms of various genera (incFuding the curious 
Heliopsyehe in its spiral tube of sand grains), Amnieola, Valvata triearinata and V. 
sincera, Sphcerium, leeches, planarians, etc., and a few Entomostraca. A fine Pluma- 
tella occasionally occurred encrusting the stems of weeds in shallow water. 
The ordinary Uniouidm of these waters were Unio luteolus and Anodonta footiana, 
both of which were very abundant. 
In the surface net occurred immense quantities of a helmeted Daphnia with head of 
truly monstrous size, sometimes larger than the body, apparently the Daphnia kerusses 
of Cox, rather imperfectly described and figured t from Fox River, the general out- 
let of this chain of lakes. With this were also many Daphnias of a species appar- 
ently new. Associated with these were frequently found large numbers of Lepto- 
dora hyalina, a few Cyclops^ Diaptomus, and Dpischura, occasional larvae of Ghirono- 
nius and Corethra, \ examples of Daphnella and of water-mites (Hydrachnidae), and 
immense and astonishing quantities of a shelled flagellate infusorian, Ceratium longi- 
corne, with now and then the curiously similar rotifer, Anurea longispina. These mi- 
nute forms fairly lined the net, and clouded the alcohol in which the specimens were 
preserved. 
If any useful comparison of the biological conditions prevailing in Lake Mendota 
during these two years may be made on the rather slender basis of my collections, it 
would lead to an inference that invertebrate life was very much more abundant iu 
1885 than in 1884, and would suggest an over population of the lake in the latter year 
which had greatly reduced the usual food of fishes of indiscriminate carnivorous habit. 
The vast abundance of the perch especially, iu this lake, is shown by the fact that 
they formed nearly the whole product of three hauls made with the seine in 1885, not- 
withstanding that approximately 300 tons of this species had died here during the 
eindemic of the year before. 
*TIiis blood-red larva, so oftea mentioned, is uniformly segmented, and about 30 millimeters long. 
It bears on tbe back of the penultimate segment four clavate anal appendages about as long as the 
segment itself, and on the antepenultimate segment two pairs of similar appendages, one at the anterior 
third and the other at the posterior margin. At the posterior margin of the dorsal surface of the 
penultimate segment are two prominent chitinous tubercles, each bearing three long recurved hairs. 
The labrum bears fifteen teeth, the middle one large and blunt with a very small coherent tooth each 
side. The remaining six on each side diminish in size outwards, the inner one of the series being 
larger than the median tooth. This tooth and the second are very closely united, the others free. 
The antennae are five-jointed ; the first joint cylindrical, stout, and very long, more than twice as long 
as the other four taken together. It bears articulated to its inner distal margin a long spine, lobed at 
tbe base, and as long as the remainder of the antenna. The next joint is also cylindrical, and about 
one-fifth as long as the first; the third joint is thick and short; the fourth longer but more slender ; 
and the last minute. 
t Amer. Monthly Micros. Jour., Vol. iv (1883), p. 88. 
j: Our collections were all made by day. 
Bull. U. S. F. 0., 88 31 
