214 



LESLIE B. AREY AND W. J. CROZIER 



TEMPERATURE 

 IN DEGREES 

 CENTIGRADE 



15° 



20° to 35' 



38° 



40° 



to contract rhythmically at intervals of 5 to 8 sec, continuing 

 in this way for 2.5 min.; the gills of the two sides did not beat 

 synchronously, but the plumes of either side alone were at first 

 more or less coordinated, the unison of the 'beats' becoming 

 less after 2 min. Foot exhibited few or no spontaneous contrac- 

 tions, but was much extended, exposing the ctenidia. The ani- 

 mals as a whole insensitive to touch. 



No contractions of the ctenidia; a few smooth contractions of the 

 foot and slight movements of the palps for several min. Ani- 

 mals normally extended. Tactile responses subnormal. 



All responses normal. 



General sensitivity ('reactivity') slightly increased during the 

 first few minutes. No spontaneous movements of the foot or 

 palp. Sensitivity to touch rather quickly decreased, but still 

 present (feeble on the ctenidia) after 45 min. Animal could not 

 close the shell when stimulated (note that at higher temperatures 

 the shell upon immersion shows a tendency to open, if it had 

 been closed, i.e., rolled up). 



If shell is rolled up, it opens. Spontaneous writhings of the 

 foot either absent or lasting 3 to 5 min. Ctenidia in some cases 

 contract for 1 min., irregularly. For 1 to 2 min., ctenidia and 

 other parts are extremely reactive to touch. Tactile re- 

 sponses gradually decrease; at first, a single stimulation of the 

 foot (after spontaneous movements have ceased) induces sev- 

 eral irregular contractions; after 30 min., foot alone is slightly 

 responsive to single or repeated touches; but irregular con- 

 tractions producing a welt result from moving a pointed rod 

 over the surface of the foot. After 1 to 1.5 hour, still in same 

 condition. 



Violent contractions of the foot for 1.5 min.; then ceased. After 

 3.5 min., all contractions ceased, and no tacile responses were 

 obtainable. 



If shell was rolled up when immersed, it opened; few, and no suc- 

 cessful, attempts to close the shell. Foot thrown into irregular 

 contractions, originating as local puckerings, which spread 

 rapidly, lasting for 2 to 2.5 min. These contractions not so con- 

 vulsive as at 42°. 



After 1 to 5.5 min. (in one case following tests for tactile sensi- 

 tivity) a second series of weak contractions of the foot appeared 

 and lasted for 2 min. The shell plates moved slightly back and 

 forth. 



In one instance there were a few irregular but widespread con- 

 tractions of the ctenidia, in which each filament appeared to act 

 more or less independently. 



42= 



43° 



