108 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



swimming movements in response to natural or 

 ganglionic stimulation. And, as already observed, 

 this peculiarity of the excitable tissues is also well 

 marked in the case of the artificial stimulation of 

 degangiionated specimens under otherwise similar 

 conditions. 



One further experiment may here be mentioned. 

 Having split open the paralyzed bell of Sarsia along 

 the whole of one side from base to apex of the cone, 

 I suspended the now sheet-like mass of tissue by 

 one corner in the air, leaving the rest of the sheet 

 to hang vertically downwards. By means of a 

 rack-work support I now lowered the sheet of tissue, 

 till one portion of it dipped into a beaker filled 

 with a solution of glycerine of appropriate strength. 

 After allowing this portion to soak in the solution 

 of glycerine until it became slightly opalescent, I 

 dropped the entire mutilated bell, or sheet of tissue, 

 into another beaker containing sea-water. If the 

 exposure to the glycerine solution had been of 

 sufficient duration, I invariably found that in the 

 normal sea-water the rhythmic movements were 

 performed by the whole tissue-mass quite as 

 efficiently as was the case in my other experiments, 

 where the whole tissue-mass, and not merely a por- 

 tion, had been submitted to the influence of the 

 irritant. But on now suddenly snipping ofl[' the 

 opalescent portion of the tissue-mass, i.e. the por- 

 tion which had been previously alone submitted to 

 the influence of the irritant, all movement in the 

 remainder of the tissue-mass instantly ceased. This 

 experiment I performed repeatedly, sometimes ex- 



