PHYSIOLOGY OF SYNAPTULA HYDRIFORMIS 363 



none of the several holothurians which he tested seemed to be 

 ''equipped with anything which might properly be called a 

 temperature sense." Kafka ('14, p. 214) dismisses the subject 

 with little more than the statement, "Die Holothurien scheinen 

 fur Temperaturanderungen ziemlich unempfindlich zu sein." 



b. Observational. Synaptula hydriformis evidently possesses 

 only a feeble temperature sense. If a half cubic centimeter 

 of water at any temperature between 14 and 42 C. is allowed 

 to flow gently from a pipette upon the tentacles of a Synaptula 

 immersed in sea-water of a temperature of about 27C., there 

 is no response. But water at 10 or less, and at 46 or more 

 thus applied, invariably causes the animal to respond. Table 

 5 gives the percentages of responses for these and other 

 temperatures. 



TABLE 5 



The effect of 0.5 cc^ sea-water at different temperatures flowing on tentacles 



A second method used in testing the temperature sense was 

 that of carefully lifting a Synaptula out of water at 27C. (the 

 normal) and suddenly immersing it in water at the desired 

 temperature. The animal was allowed to remain 3 minutes 

 at the given temperature and then carefully returned to water 

 at 27. Table 6 gives the results of such trials. 



Here the limits between which there were no responses were 

 20 and 40. Beyond these limits one or more vigorous contrac- 

 tions of the whole body were given, followed by relaxation at 

 the higher, and partial contraction at the lower temperatures. 

 To produce death in 3 minutes a temperature of 46 was 

 necessary. 



