SUMMARY 81 
abundant and evenly distributed throughout the deep-water belt. The 
principal invertebrates are Pontoporeia hoyi, Mysis relicta, water-mites, 
midge larvae, and a species of Pisidium. 
The fish, however, show some noteworthy peculiarities of distribution. 
The lake trout rarely leaves this belt, except during the breeding season. 
The blackfin (Argyrosomus nigripinnis) is below 70 meters, except in 
December, when it has been recorded in 60 meters. Hoy’s whitefish 
REPRESENTATIVE CRUSTACEANS OF THE DEEP-WATER COMMUNITY OF 
LAKE MICHIGAN 
Fic. 22.—A schizopod (Mysis relicta); enlarged as indicated (after Smith). 
Fic. 23.—An amphipod (Pontoporeia hoyi) (after Smith). 
(Argyrosomus hoyi) is rare, and Triglopsis thompsoni has not been 
recorded above 115 meters; all accordingly live under uniform condi- 
tions—no day, no night, no seasons. 
Ill. Summary 
The available data on the conditions and life in the lake are of such 
a nature as to justify few conclusions of weight. We find only hints 
here and there which may be useful to those who shall investigate the 
lake in the future. 
1. Bottom forms are the most abundant on the open shores which 
are rocky, and which form good substrata for the attachment of algae 
and the holdfast organs of animals. 
