THE ACTIVITIES OF CORYMORPHA 307 



tone till it no longer responds to stimuli through its neuro- 

 muscular apparatus, it will still discharge its nettling filaments 

 on stimulation with weak acid. It, therefore, seems clear 

 that the nettle cells respond to direct stimulation and are not 

 under the control of the nervous system, a conclusion that sup- 

 ports most of the recent work on this question in the hydro- 

 zoa (Wagner, '05, and Hadzi, '09, on Hydra; Lipin, '11, on 

 Polypodium) . 



The muscles of Corymorpha are few and simple in comparison 

 with those of an actinian (Parker, '16) and have already been 

 briefly described by Torrey ('04 a, p. 403). The longitudinal 

 muscle of the stalk (Allman, '63, p. 3; 71-72, p. 209) is a sh 3 et 

 of tissue whose fibers run lengthwise that structure and are 

 closely applied to the ectodermic face of the supporting lamella. 



The circular muscle of the stalk (Allman, '63, p. 4) consists 

 of a sheet of fibers applied to the entodermic face of the sup- 

 porting lamella and extending at right angles to those of the 

 longitudinal muscle. Near the distal end of the stalk there is 

 usually a marked constriction, which is apparently brought 

 about by the excessive contraction of the circular muscle fibers 

 of that region. This constriction suggests the presence of a 

 specialized muscular sphincter, such as has been claimed by 

 Riddle ('11, p. 390) in Tubularia, but as I was unable to identify 

 in section a special accumulation of fibers in this region, it seems 

 scarcely appropriate to describe a sphincter muscle as distinct 

 from the rest of the circular muscle of the stalk. 



An ectodermic longitudinal muscle and an entodermic cir- 

 cular one occur in the proboscis exactly as they do in the stalk. 

 In both the proximal and distal tentacles longitudinal ecto- 

 dermic muscles can be seen in sections. I have failed, however, 

 to identify in the two sets of tentacles the circular entodermic 

 muscles mentioned by Torrey ('04 a, p. 403). If they are 

 present, they must be relatively poorly developed, for in mate- 

 rial in which the longitudinal fibers could be clearly demonstrated, 

 the circular fibers could not be seen though the plane of section 

 was entirely favorable for this purpose. I have, therefore, 

 been able to identify at most only six muscles or groups of 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 24, NO. 2. 



