136 ON THE PHTSIOLOGT OP ECHINODERMATA. 



of the animals gape widely asunder. Soon afterwards spon- 

 taneity and irritability are entirely lost. Prolonged exposure 

 kills. 



5. Alcohol. — The effects of alcohol are closely similar to those 

 of chloroform, although the torpidity produced is not quite so 

 complete. 



6. Strychnia. — On adding some crystals of the sulphate to 

 sea-water the first effect on the Echini was that of making their 

 spines extend rigidly in their radial planes, which gave a striking 

 rosette appearance to the animal. They seemed to be in a state 

 of strain, for though they responded rapidly and strongly to 

 stimulation, they sprang back to their original position so soon 

 as the stimulation was discontinued. On being inverted the 

 animals were unable to right themselves ; and on being restored 

 to normal sea-water, the spines retained their rosette arrange- 

 ment for many hours. On faintly acidulating the water so as 

 to secure a better solution of the alkaloid, the effect on the 

 spines was that of throwing them into great disorder, while all 

 spontaneity and irritability were destroyed. The animals were 

 killed. 



7. Nicotin. — A small trace of this substance added to the 

 sea- water is sufficient to determine the speedy death of the 

 Echini exposed to its influence, the spines being thrown into 

 great disorder. 



8. Curare (powder rubbed up with a few drops of spirit and 

 distilled water before being added to the sea-water). — The Echini 

 soon became motionless, lost their irritability, but adhered firmly 

 with their pedicels to the floor of the tank, and when forcibly 

 detached again resumed their hold. After a time the animals 

 appeared to be dead, the spines being stiffly depressed but not 

 in disorder. On being transferred to normal sea-water, how- 

 ever, their recovery was rapid and complete. 



9. Digitalis. — After exposure for some time to the influence 

 of Digitalis, the Echini lost all their spontaneity aud irritability, 

 being therefore to all appearance quite dead ; but on being then 

 restored to normal sea-water, they partly recovered. Next day 

 they were found to be moving very languidly, their pedicels not 

 adhering to the tank, and their general irritability being much 

 impaired. 



10. Cyanide of Potassium. — For some time after immersion in 

 a very diluted solution of this substance the Echini ajipeared to 



