306 G. H. PARKER 



of the animal but by cilia. In all the many tubes that I have 

 examined the motion is a surging back and forth and is never 

 local in character. I have never seen any spots in the tubes 

 where local activity could be identified and since the surging 

 of the fluid is fully accounted for by adjustments to muscular 

 pressure, I suspect that there are no cilia even in the interior 

 of Corymorpha. This species therefore, seems to be entirely 

 devoid of these organoids. 



Nettle cells, the third type of effector, are well developed 

 in Corymorpha. Their presence can be easily demonstrated 

 under the microscope by flooding a given piece of living tissue 

 with dilute acetic acid, whereupon their filaments are freely 

 discharged. They can thus be shown to be generally scattered 

 over the stalk except that they are more abundant on the distal 

 naked portion of this structure than on that part which is cov- 

 ered with perisarc (Torrey '02, p. 38; '07, p. 279). They are 

 also found on the proboscis and the peduncles of the fixed me- 

 dusae, but I have never seen them on the medusae themselves. 

 The tentacles are abundantly supplied with them. They are 

 especially numerous near the tips of both the proximal and the 

 distal tentacles. In these situations two types of nettle cells 

 can be distinguished, those with long filaments, about 0.15 mm. 

 in length, and those with short filaments, 0.025 to 0.04 mm. in 

 length. 



The nettle cells of Corymorpha, like those of the antho- 

 zoan polyps (Parker, '16, p. 463), appear to be quite indepen- 

 dent of nervous control. If a stimulating fluid, such as ten 

 per cent acetic acid, is deeply colored and allowed to creep 

 over a live proximal tentacle of Corymorpha while the tentacle 

 is being watched under a microscope, the nettle cells will be 

 seen to discharge their filaments only where they are covered 

 by the stimulating fluid and never in advance of this. When 

 such a tentacle is mechanically pressed, the discharge takes 

 place only in the region of pressure. These strictly local re- 

 sponses suggest non-nervous action, a view that is confirmed 

 by the use of anesthetics. After a tentacle of Corymorpha has 

 been treated with a solution of magnesium sulphate or of chlore- 



