Sensory reactions of Holothuria surinamensis. 279 



Much peristalic activity of the body muscles evident; waves 

 beginning at any level run anteriorly and posteriorly with 



■33*^ J about equal frequencies. 



35" 1 In only a few instances is more than one wave of con- 



traction apparent at a single instant. Sensitivity tu mechanical 

 stimuli much lessened. 



-36** Localized swellings begin to appear on the body wall. 



{Cloacal aperture closed by contractions of its sphincter. No 

 reaction to mechanical stimuli by any part of the body. 

 Animals begin to shorten the long axis, finally assuming an 

 ellipsoidal shape. Tube feet, tentacles, etc., retracted. 

 . , f,Q fBody begins to whiten underneath the pigment, owing to the 

 aqo { coagulation of the muscle proteins. In most cases (7) this 



[ whitening began at the posterior end. 



{Animals assume a bloated appearance, the body wall thinning 

 out in several places, then collapsing. Dead.^) No muscular 

 rigidity. 



For producing temperatures below 27*^, beakers of sea water 

 were surrounded by cracked ice. At about 15*^, the pedicels and 

 tentacles were retracted, but in some cases the latter were re-ex- 

 tended. No shadow reactions were obtained below 5**. At 3*^ the 

 animals had the appearance of being anaesthetised; they did not 

 move, nor could any reactions be obtained from them ; recovery from 

 a half hour's experience of this temperature was rapid, the animals 

 becoming normal again in about twenty minutes. 



Other experiments consisted in plunging the holothurians, par- 

 tially or entirely, into sea water at temperatures remote from the 

 normal. When thus suddenly transferred to water kept at 3*^, no 

 special reaction was evident; in most cases the tentacles and pedi- 

 cels slowly expanded, but reacted only very faintly to pinching with 

 forceps, etc. Recovery on return to the normal temperature was 

 rapid, as in the previous tests. Upon sudden transfer from 27° to 

 water at 40°, the effect comprised vigorous general muscular con- 

 traction (in a few instances producing visceral autotomy) and the 

 coagulation of the muscle materials, death following within five 

 minutes. At 45° instantaneous whitening and death were the result. 

 If merely the anterior or posterior end of an individual were thus 

 treated, no movements were made by the animal to withdraw the 

 •affected part from the heated or cooled water. Tests for thermo- 

 taxis were then made by placing the holothurians in various posi- 



1) Frenzel (1885) states that "Holothtiria" died in serval hours at 

 -30 — 40°, when suddenly subjected to that temperature. 



Zool. Jahrb. XXXV. Abt. f. allg. Zool. u. Pliysiol. 19 



