280 SELIG HECHT 
TABLE 1 
Opening times for replaced animal 
TIME SECONDS 
10: 10 1225 
10: 19 14.8 
10: 30 14.3 
10: 42 14.4 
PAV ETAL Go Saas a usm Saat nce eee 14.0 
ture would result in its remaining closed, or in its opening time 
being prolonged. Neither expectation was realized. Instead, 
the siphons opened in the same time as in seawater at room tem- 
perature. The above animal, when placed in seawater at 35.5°C., 
opened in 14.2 seconds; and in water at 42.0° it opened in 13.9 
seconds. Animal VII.18.2, experimented with at the same time 
as VII.18.1 gave the following similar results (table 2). 
TABLE 2 
Opening times of replaced animal at different temperatures 
TIME TEMPERATURE OPENING TIME 
seconds 
10: 13 26 vin 725 
10: 25 26 isa 10.5 
10: 35 ABST 9.0 
10: 50 26.7° 9.0 
11: 10 3020 8.5 
11: 30 40.0° 7,8 
The further history of the animals in this experiment, how- 
ever, is significant. In the seawater at the higher temperatures 
the siphons opened slightly after the usual interval, but at once 
closed with a jerk. After a few seconds the siphons again opened 
only to be shut immediately, and accompanied, as before, with 
a partial ejection reflex. . 
The conclusions from these results are evidently that A. atra 
is sensitive to a temperature change, that the receptors are lo- 
cated within the siphons, and that the test and siphon rims are 
insensitive to this quality of stimulation. 
