EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
133 
the grounds. (See accompanying report of McMillin.) Further, the oysters 
remaining were extremely thin and watery, showing none of the rich white meat 
of normal specimens. Also, new shell growth was seldom to be observed. These 
four characteristics may be reduced to three for the present purposes by combining 
lack of reproduction with thinness of meats, for the former is probably largely a 
consequence of the latter. However, it is probable that liquor may be highly toxic 
to oyster larvse. It would be of considerable significance to determine whether 
these conditions could be reproduced among oysters in the laboratory by adding 
sulphite liquor to otherwise favorable water. In the following pages are descriptions 
of experiments designed to determine the potency of the liquor in these respects. 
A short description of the feeding activities of oysters is necessary to make the 
experimental results clear. (See Galtsoff, 1926, 1928.) 
The oyster shell consists of two halves, or valves, connected by an elastic hinge 
which holds the valves several millimeters apart. The adductor muscle of the 
oyster is attached to both valves and, by contracting, closes them. Feeding can 
take place only when the muscle is relaxed and the valves open, for only then can 
the food-bearing water enter. The four gills of the oyster force the water through 
themselves by ciliary action (see accompanying report of Galtsoff) and filter out 
the food organisms, which are then swallowed. It is clear that under otherwise 
identical conditions two oysters may be together, one remaining open most of the 
time and the other remaining closed most of the time, the former would have oppor- 
tunity to take in more food than the latter and would consequently be expected 
to store up a larger reserve food supply, which in the oyster is chiefly glycogen. 
The so-called fat oyster contains a large supply of glycogen. Relative absence of 
this reserve causes an oyster to be thin and watery, as has been the case with the 
Oakland Bay oysters. 
Any agent which reduces the number of hours per day that the valves of oysters 
remain open at the same time reduces the number of possible feeding hours. Such 
oysters would be expected to store up less reserve food. The present experiments 
were designed to show whether the presence of sulphite liquor causes oysters to 
reduce their possible feeding time by remaining closed longer than specimens in 
uncontaminated water. 
Following are detailed descriptions of the behavior of each experimental speci- 
men. In general, a single series consisted of two experimental pairs of oysters, 
in different concentrations of liquor, and one pair of control specimens in uncon- 
taminated water. Because of large individual variations it is difficult to express 
the results in any manner other than as separate descriptions. The series are 
organized according to concentrations of liquor employed, but there is considerable 
overlapping. 
Concentrations of liquor in water are stated as parts per thousand. It must be 
emphasized that the stated concentrations represent the mixtures which the appa- 
ratus was standardized to deliver, and that any variations from this would be due 
to stoppage of the liquor tubes, causing temporarily a lower concentration. The 
water system was readily kept constant but, because of suspended matter in the 
liquor, there was an occasional slowing in its rate due to accumulation of particles 
in the small opening of the stopcock. This was reduced to a minimum by frequent 
cleanings, but any error due to this would tend to make the concentration lower, 
not higher, than that stated. 
