INVERTEBRATES OF LAKES GENEVA AND MENDOTA. 
479 
10. Episehura lacuatris. A very few. 
11. Diaptomua gracilis. Oaly one specimen. 
12. Ophrijdium,sp. A single colony. 
A haul of the to wing-net in swift water at the mouth of the inlet, made at 9 p. m., gave the follow- 
ing list : 
1. Corethra, sp. A few pupae about ready to emerge. 
2. Corixa,ap. Several young. 
3. Ephemeridce, The collection was largely com posed of larvie of this family, mostly of the genus 
Ccenis. One dissected, had filled the alimentary canal with fine dirt, containing a few fila- 
ments of Algae and occasional diatoms. Other larvm were allied to Callibwtis of Eaton’s Mon- 
ograph. The palpi of the first and second maxilliB had, however, but two joints each. One 
ally of Ecdyurus was also noticed. 
4. Hydrachnidw. Several examples. 
5. AUorchestes dentata. A single one. 
6. Daplinia retrocurva, var. A few. 
7. Sida crystallina. Several examples. 
8. Cyclops, sp. Occasional examples ; not determined. 
9. Epischura lacustris. Several specimens. 
10. Limnodrilua sp. A single specimen of this mud worm. 
A small collection made by turning stones in the water along the shore gave sev- 
eral larvae of Psephenus, probably lecontei, but differing noticeably from Kellicott’s figure 
of that curious and interesting animal, as given in the “ Canadian Entomologist,” Vol. 
XV., p. 191. A GcBnis nymph, another of the Ecdyurus group, and a phryganeid pupa 
in its sand tube, were the only other insects. A single fresh water shrimp {Palcemonetes 
exilipes) was taken here, together with a few examples of Oammarus — possibly young 
of fasciatus, but too small for determination. Also AUorchestes dentata, a single Gor- 
dius, and several small leeches. 
It is evident from the foregoing that even in a lake of so moderate size as this, the 
smaller inhabitants are quite clearly divided into pelagic and littoral groups, the lat- 
ter containing the greater number of species, but the former not less numerous in in- 
dividuals; and a comparison of the results of dredgings shows that this difference ap- 
plies to the animals of the bottom as well as to those swimming freely above it. 
This pelagic group of Entomostraca includes Leptodora hyalina, Daphnia retrocurva, 
and Epischura lacustris, as its principal species, Diaptomus sicilis, another pelagic form, 
being, apparently, not very abundant in this lake ; while the characteristic animals of 
the bottom of the interior parts of the lake are Pisidium adamsi, a large red Ghironomus 
larva, and a species of Limnodrihts — both this worm and the larva just mentioned 
making tubular burrows in the mud. 
It is also apparent from the product of the towing net in deep water under varying 
conditions, that the pelagic Entomostraca avoid the surface by day, whether it be rough 
or calm, or the weather cloudy or clear ; but that they do not necessarily withdraw to 
any great depth — hauls 10 feet below yielding “ good” or “ large” collections when 
the sun was shining. By night, on the other hand, the yield at the surface was large, 
even in a high wind. 
LAKE MEND OTA. 
I first visited LakeMeudota in August, 1884, at the request of Prof. S. F. Baird, 
U. S. Commissioner of Fish and Fisheries, for the purpose of making a study of a most 
remarkable mortality among the fishes of a single species in the lake — the common 
perch (Perea Jiavescens Mitch.). 
