Freshwater Mussels Zon 
Obstacles on the bottom divert a mussel from its course. In the 
lake or in slight current the original course is often not resumed; but 
in a brisk current the mussel tends to fall back into the same angle 
with the flow of water regardless of what that angle may have been. 
Obstacles may include an alternation of sand, gravel, and mud. Drift- 
wood, plant roots, rubble, or stones are the more obvious ones. The 
concave walls of an aquarium may be followed a little way, but will 
soon bring the mussel to a halt. Ripple marks upon sandy bottom may 
be seen to have diverted a mussel more or less shoreward. 
The prevalence of mussels upon favored type of bottom is in itself 
an argument for greater or less migration. Juveniles do not remain 
where left by their fish hosts at random, but find their way to suitable 
substratum. 
Besides the common lake species there occurred in the outlet not far 
below the dam the following additional: Symphynota costata, Quadrula 
undulata, and Lampsilis anodontoides. Quadrula plicata doubtless oc- 
curs; it has been mentioned that one individual has been taken in the 
lake. 
MISCELLANEOUS OBSERVATIONS. 
In addition to the production of a shell the Unionidae may consti- 
tute a geological agent of a sort not usually recognized. The total 
amount of water siphoned and the amount of material taken out of 
suspension are surprising. Both mud and organic matter are separated 
out and precipitated in mucous clots. An aquarium jar filled with muddy 
water is cleared entirely in the course of a few hours by a single mussel. 
Beneath the posterior end of a mussel which is actively siphoning 
in a lake the ground may be seen to be carpeted with a conspicuous 
amber-green slimy coating. 
Due to the considerable deposition of marl on the plant grown ter- 
race, through the reduction of the bicarbonates to carbonates in photo- 
synthesis, there is much less lime present in the water of the outlet of 
Winona Lake. Prof. Scott has determined the carbonate ratio to be about 
thus: Springs : upper lake : outlet :: 3:2: 1. 
The writer compared the total weights and shell weights of 16 
Lampstlis luteolus from Dickey’s Point in the lake with an equal number 
from Walnut Creek. The results follow: 
From lake From outlet 
Average length 90.8 mm. 87.4 mm. 
Average weight 127.0 gm. 107.0 gm. 
Average shell weight 69.0 gm. 51.0 gm. 
Ratio shell to total weight 54.0% 48.0% 
The lake specimens were heavily encrusted with the usual marl ‘de- 
posit, and were cleaned for comparison. The total weights were then taken 
with the mantle chambers full of water. The number used was small, 
hence subject to error. The matter will be followed further. So far as 
the present data go we have a significant difference due to either the 
lime content of the lake, or to some other factor. This difference in 
shell weight amounts to six per cent of the total weight of the body, or 
about twelve per cent of the shell weight itself. Comparative data 
are not yet available from lakes of greater or less hardness. 
