Sensory reactions of Holothuria surinamensis. 285 



11,20 50 Oneother animal eviscerating; considerable longi- 



tudinal folding of the body wall in all. First 

 evisceration complete. 



11,40 70 Two more dead. 



11,55 85 All dead, in the extended state, with the tube 



feet, etc., withdrawn. 



One noteworthy result of Expt. 82 is the rapid solution of the 

 integumentary fluorescent pigment by fresh water; this effect would 

 form a very convenient indicator in studies of permeability changes. 



Mixtures of sea water and rain water in the proportion of 1 : 1 

 gave no reactions. Sea water concentrated to 0,5 its original 

 volume^) and reaereated by splashing did produce reactions from all 

 parts of Holothuria save the tube feet and papillae. The reactions 

 were of very slight amplitude, and I believe are to be accounted 

 for, not by the increased osmotic pressure of the stimulant, but 

 rather by the disturbance of the normal electrolyte balance in sea 

 water with changing concentration; Spaeth (1913, p. 540) found 

 that diluted sea water stimulated Fundulus melanophores through 

 the preponderance of the sodium-ion. Another source of error in 

 these measurements arises from the fact that the water currents 

 from the pipette might also serve as a tactile stimulus. Eepeated 

 treatment with M/10 KCl, for example, so sensitized Holothuria! s, 

 integument that it did react to currents of fresh water, and even 

 to those of sea water. Jennings (1907, p. 69) found a similar inter- 

 relation of chemical and tactile reactions in the pedicellaria rosettes 

 of Asterias forreri. Accordingly, a sufficient period of rest (five min- 

 utes) was allowed between successive stimulations, and frequent 

 •control tests were made with the rain water alone. Tables XIII 

 to XIX, inclusive, summarize the results of these experiments. Each 

 of the reaction-time figures is the mean of from ten to fifteen meas- 

 urements made on three to five animals, the agreement between 

 the individual measurements being sufficiently close to warrant the 

 use of this comparatively small number of measurements and animals 

 for the purpose of a general investigation. The several random 

 •examples given in Tables XI and XII will serve to emphasize this 

 point. A few other substances tested qualitatively will be referred 

 to in the discussion. 



1) Bermuda sea water normally contains about 36,5 parts of salt 

 per 1000 (Maek, 1913). 



