314 G. H. PARKER 



tentacles (Torrey, '04 a, p. 399) ; the proboscis is also very likely 

 to turn in the direction of the stimulated tentacle, and the 

 distal tentacles may likewise become active. To a still more 

 vigorous stimulus not only do the parts of the hydranth re- 

 spond, but the stalk may contract (Torrey, '04 a, p. 400). Thus 

 impulses to motion may spread from a single proximal tentacle 

 to any part of the body. The same is true of the proboscis 

 and of the distal tentacles Conversely, by stimulating the 

 stalk, responses can be called forth from both sets of tentacles 

 (Torrey, '04 a, p. 401). These observations indicate a diffuse 

 type of transmission, such as is generally assumed for a nerve- 

 net. It is also clear that the stronger the stimulus the more 

 distant the effector that can be activated. 



To ascertain something of the nature of the transmission, 

 several kinds of experiments were tried. When a polyp of 

 Corymorpha is anesthetized for a few minutes with magnesium 

 sulphate or chloretone, all responses of tentacles, of proboscis, 

 and of stalk disappear except the slow formation of constric- 

 tion rings in the stalk. The responses thus eliminated may be 

 made to return by placing the polyp for three or four minutes 

 in pure sea-water. Since the effectors that are rendered in- 

 active are the ectodermic musculature and since the drugs used 

 are known to act chiefly on nervous tissue, the conclusion is 

 drawn that the essential part of the nervous mechanism of these 

 animals must be in their outer layer, the ectoderm, a conclusion 

 supported by the very short time needed for anesthesia as well 

 as for recovery from this state. It, therefore, seems probable 

 that nervous transmission in Corymorpha is an affair of the 

 ectoderm. 



To test this view, a polyp about ten centimeters in length was 

 put horizontally in an aquarium and pinned at the middle of 

 its length to a slight elevation of wax so that its foot-end and 

 its hydranth projected for some distance horizontally and freely 

 into the surrounding water. On applying a faradic current to 

 the hydranth, the foot-end contracted together with the rest of 

 the stalk ; on applying it to the foot-end the hydranth contracted 

 together with the rest of the stalk. The polyp" was now un- 



