AUTOTOMY IN HOLOTHURIANS. 45 



chemicals were injected into the body cavities of two hundred 

 and forty-six holothurians. Thyone briareiis was the only species 

 used for these experiments, and the animals selected were of 

 medium size, measuring from five to eight centimeters in length. 

 As the normal reactions of this species have been described in a 

 former paper (Pearse, : 08), they will not be considered in detail 

 here. Twelve individuals were experimented upon at one time, 

 and they were placed in pairs in six finger bowls which contained 

 sea water. The substance to be tested was injected into the body 

 cavities of ten individuals by means of a hypodermic syringe. 

 The two remaining animals were pricked with a needle without 

 having anything injected into them and served as a control. Ob- 

 servations extended over a period of twenty-four hours in each 

 case. Experiments were started in the morning and observations 

 were made at intervals during the same day. The condition of 

 the animals on the following morning was also recorded. 



The results of the experiments are set forth in Table I. A 

 volume of distilled water which exceeded that of any of the other 

 substances used was injected into ten individuals and they were 

 apparently unaffected by it. It was therefore assumed that the 

 effects obtained in the other experiments were due to the specific 

 substances which were injected. 



Substances like acetic acid and clove oil, which were apparently 

 highly irritating and caused the most intense contractions of the 

 muscles of the body-wall, did not bring about the ejection of the 

 visceral organs. Nor were drugs like codene and atropine, which 

 caused violent peristaltic waves of contraction to pass over the 

 body, any more potent in inducing autotomy. The same may 

 be said of sodium chloride, atropine and clove oil, although the 

 injection of any of these substances was often followed by a 

 waving of the oral tentacles to perform "feeding" movements, 

 thus bringing about favorable anatomical relations for autotomy. 

 All the reactions induced by the substances mentioned indicated 

 violent stimulation or great bodily activity, but none of them pro- 

 duced any increased manifestation of self-mutilation. 



The injection of strychnine was followed by the largest per- 

 centage (35) of cases of autotomy and methylene blue came next 

 (22 per cent.). Strychnine apparently caused a great increase in 



