THE ACTIVITIES OF CORYMORPHA 313 



stalsis, but ordinarily this muscle, like that of the stalk, prob- 

 ably responds only to direct stimulation. 



The four ectodermic muscles, the longitudinal muscles of 

 the stalk, of the proboscis, and of the two sets of tentacles, 

 are relatively quick in action and cease to respond under the 

 influence of anesthetics. These are probably controlled by a 

 nervous system composed of ectodermic sense-cells and a nerve- 

 net, such as is commonly met with in many coelenterates (Wolff, 

 '04; Hadzi, '09). 



Of the effectors of Corymorpha the muscles are the only 

 elements that are under nervous control, a condition that sup- 

 ports the conclusion of Lipin ('11, p. 417), that in the hydroid 

 Polypodium aside from the muscles no other histological ele- 

 ments are dominated by the nervous system. 



3. NERVOUS TRANSMISSION 



In attempting to study nervous transmission in Corymorpha 

 various stimuli were first tested. Corymorpha, like Tubularia 

 (Pearse, '06, p. 406), is apparently quite uninfluenced by light 

 (Torrey, '02, p. 39; '04 a, p. 405). Though heat and some 

 chemicals are stimulating (Torrey, '04 a, p. 401), these means 

 of inducing reactions are not so easily controlled as mechanical 

 stimuli (Torrey, '02, p. 41). But even here a tremor may be 

 transmitted from the part of the body touched to a distant 

 receptor and thus call forth deceptive responses. I, therefore, 

 resorted for stimulation to a weak faradic current; the elec- 

 trodes for this could be set in place and, after all possibility of 

 accidental mechanical disturbance had passed, the intended 

 stimulus could be applied by simply making the current, thus 

 avoiding any complication from possible tremors. A well local- 

 ized and controllable stimulus was thus obtained. 



If a proximal tentacle of Corymorpha is gently touched by 

 a blunt glass-rod or stimulated by a very weak faradic current, 

 it will in a second or so after the application of the stimulus 

 bend rather quickly toward the proboscis, after which it will 

 slowly return to its resting position. A more vigorous stimu- 

 lus will excite to action not only one but many of the proximal 



