640 JAMES L. KELLOGG 
The second muscular movement clears the palp surface even 
more swiftly, and is usually put in operation when an exceptionally 
large amount of material appears on the folds. It consists in a 
rolling upward of the ventral margin—or a part of it—until the 
mass on the folds is touched and lifted off. More often, in other 
forms than Schizotherus, in which the lateral part of the palp is 
continuous with the vascular fold, the palp is contracted into a 
spiral, folded face outward, so that parts of the ventral margin 
touch all surfaces of the palp; and, while thus twisted, the whole 
is rapidly cleaned of every particle adhering to it. Everything 
quickly reaches the tip, and is thrown off. 
Large collections of the outer demibranch are usually taken 
directly from the distal groove which runs down anterior to the 
inner, by cilia of the mantle anteriorly, as will be described in 
other forms. If, however, more than an extremely small amount 
of material is placed in the lateral groove between the palps, 
some of it touches the ventral margin, and all is carried away. 
Oral objection has been made to my contention that oysters 
are able to feed only when waters that they inhabit are compara- 
tively clear. This is based on the fact that waters on certain 
oyster fields are sometimes muddy for long periods, and also 
that in waters frequently muddied, there are found, at times, in 
the stomach contents so many more sand grains than diatoms, 
that the latter cannot be counted. The conclusion therefore is 
that oysters feed normally in muddy waters. 
It may be answered that no one has ever determined in the 
periods during which oysters are known to have grown—the 
summer months in the North—the duration of the times in which 
waters have been turbid or comparatively clear, nor at any time, 
the amount of turbidity. Changes in the amount of suspended 
matter in all waters, salt or fresh, are frequent, and especially 
along seashores everywhere, for here wave and tide action make 
themselves felt. Very marked changes in the degree of clarity 
may be observed almost daily, even in the small, sandy-bottomed 
lakes of Florida, in which, if anywhere, one might expect con- 
stancy in this respect. The subject has not been studied care- 
fully. From my own general observations, I believe that the 
