EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
157 
the series (fig. 38) shows the two records of the experimental oysters as straight lines. 
All movement has ceased and they are gaping wide open, motionless. 
In the experiment just described, the different phases of the oyster’s death process 
followed upon one another within a few days. In tests in which lower concentrations 
of sulphite liquor were employed, much longer periods of exposure were required before 
the specimens died. (Bottom two records, figs. 34 to 38.) However, the same 
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Figure 37. — Reproduction of portion of kymograph record of experiments Nos. 24 and 25, one day later than 
that shown in Figure 36. Specimens Nos. 1 and 2 have lost their ability to close completely and move- 
ments are relatively slight and infrequent. Specimens Nos. 5 and 6, in weaker concentration of liquor re- 
main closed a large part of the time, and when open are very active. The behavior of these is similar to 
that of specimens Nos. 1 and 2 about three days previously, as shown in Figure 35 
sequence of the different phases of the activity of the oysters during treatment was 
observed to hold, although each phase was very much prolonged. 
The most striking characteristics of the reactions before the approach of gaping 
were the tendency to remain closed for long periods and, while open, to make abnor- 
mally frequent temporary closures. If there had been a marked deficiency of oxygen, 
the specimens would have become less active from the beginning, according to the 
