THE ACTIVITIES OF CORYMORPHA 315 



pinned, bent into the shape of a U with the curve where the 

 pin had been and this part was dipped for from one to two 

 seconds into ten per cent acetic acid and then immediately im- 

 mersed in pure sea-water. As a result of this treatment the 

 ectoderm was killed in a broad ring around the middle of the 

 stalk, but the deeper tissues, at least the axial vacuolated cells, 

 were left alive. On pinning the polyp again in the horizontal 

 position and stimulating it electrically, it was found that the 

 nervous impulse never passed from one end to the other, as in 

 the first trials, but was always limited to the end at which it 

 was applied, showing that the superficial tissue of the polyp, 

 but not its core, is the part concerned with transmission. 



This experiment was repeated with the modification that, in- 

 stead of destroying the superficial tissue with acetic acid, it 

 was anesthetized with chloretone. Polyps thus treated failed 

 to transmit impulses over the anesthetized region though after 

 ten minutes in pure sea-water transmission in this region was 

 reestablished. As chloretone is known to abolish the neuro- 

 muscular activities of the ectoderm, but to leave the entodermic 

 muscles unaffected, I conclude that the parts concerned with 

 transmission are not only superficial but ectodermic. 



To determine whether there are special transmission tracts 

 in the polyp, several lines of experimentation were carried out. 

 A large polyp was split lengthwise from the hydranth end 

 through the column almost to the aboral end. Such a prepara- 

 tion has the shape of a letter V, with two half-hydranths at the 

 free ends of the V and the unsevered base at the angle. On 

 stimulating one half-hydranth with a faradic current both arms 

 of the preparation contracted though the base was outwardly 

 inactive. Hence I conclude that the base, though without 

 muscle, transmits nervous impulses from one side of the polyp 

 to the other. If the base is now locally anesthetized and the 

 experiment repeated, the contraction is found to be limited to 

 the arm of the preparation that is stimulated, thus demonstrat- 

 ing the superficial location of the transmitting tissue. 



I next tried another form of this experiment in which, how- 

 ever, the two arms of the preparation were united through the 



