280 W. J. Ceozier, 



tions along the axis of a long- narrow trough in which temperature 

 gradients were maintained by heating one end with an alcohol 

 lamp and cooling the other with an ice-pack. No marked result» 

 were obtained, it being clear that the animals were in no sense 

 oriented by the temperature conditions, nor did they tend to con- 

 gregate more at one end of the trough than at the other. 



3. Local Application of heat. 



Sea water heated to 40", 55*^ and 75*^ (the evaporation being 

 made good with rain water) was gently pipetted in five cubic centi- 

 meter volumes over diiferent regions of the body. In these tests 

 the animals were placed in small dishes containing just enough 

 water (at 26") to cover them. Even then, however, the actual tempe- 

 rature of the water which reached the holothurians' surface was of 

 course below 40", 55", etc. No reactions were obtained from the 

 pedicels, papillae, or the mid-body surface ; the tentacles, the anterior 

 end and the posterior end reacted with some vigor. In none of 

 these reactions was there any distinct bending away from the side 

 stimulated. The responses were of about the same amplitude as 

 those obtained with a vigorous current of sea water at the holo- 

 thurians' own temperature. The tentacles occasionally reacted to 

 currents of water at 3". Heated glass rods and steel needles were 

 held in close proximity to various regions of a holothurian's body 

 when it was out of water. No constant effects were obtained. In 

 some experiments the body wall was burned by touching with a red. 

 hot rod, but even then no clear-cut response was given. 



4, Discussion. 



As the result of these tests, it appears that the temperature- 

 sense, if anything properly so called is present in Eolothuria, must 

 be very poorly developed. The following effects of various tempe- 

 ratures are to be noted: 



1. 2 — 5". The anaesthetic- like actions of low temperatures. 



2. 31 — 34". The gradual cessation of the shading reactions; the 



intensity of the light and (possibly) the rate of 

 heating are factors concerned. 



3. 33 — 37". The production of muscular peristalsis at temperatures^ 



above the normal. 



4. 35 — 380. rphe stoppage of respiratory cloacal movements by the-- 



contraction of the sphincter. 



5. 38 — 41". General muscular contraction. 



