156 
BULLETIN OF THE BUREAU OF FISHERIES 
level of the record as compared with that before opening. Such a specimen is begin- 
ning to gape, the adductor muscle losing its tonus, so that the shells open wider than 
normally. The muscle also loses ability to make a complete contraction. There 
follows then a period during which gaping becomes more and more pronounced, 
A.M. 
EXP. 25. 
!0 HP™ 
V 
(SPECIMEN 1.) 
I 
12 
(SPECIMEN 2.) 
W 
PM. 
OP 
I I I 
10 II 12 
I 
I 
APRIL 21. 
(SPECIMEN 3.1 
i CONTROLS \ I 
10 J II 
12 (SPECIMEN 4) I 
I 
10 
I 
12 
(SPECIMEN 5.) 
till 
10 £XP. 24. u 12 I 
SP.R™ (SPECIMEN 6.) 
Slit 
SO II 12 I 
Figure 36. — Reproduction of portion of kymograph record of experiments Nos. 24 and 25 about two and 
one-half days later than that shown in Figure 35. The inability of specimens Nos. 1 and 2 to close com- 
pletely is shown. The record of specimen No. 1 is wavering, showing that closure was incomplete. The 
record of specimen No. 2 shows the differences in height of the lines, or differences in degree of closure. 
Specimens Nos. 5 and 6 in a weaker concentration of liquor are still more active than the controls 
complete closure never occurring, and even the partial closures become less frequent. 
(Fig. 37.) 
As the oyster gapes, the constantly less frequent shell movements are also of less 
amplitude. It will be observed in Figure 37 that the contractions are very weak, but 
that the muscle acts as if attempting to hold the shells together, instead of relaxing 
immediately after a contraction, as is typical of the control records. When the 
oysters are in this condition they are almost at the death point. The last figure of 
