GEORGE B. CHAPMAN 149 



have any other evidence that the tips of the tubules attach to the 

 prey rather than penetrate? 



CHAPMAN: I don't think there is any other evidence. There is 

 very Httle evidence on the structiue of the tubule itself, because 

 when tubules are fired they are hard as the dickens to find, and 

 when they are not fired we don't often get such sections as this one. 



HAND: How many times have you seen that hook? 



CHAPMAN: Just once. But we have other sections showing that 

 it is not an artifact. 



HAND: You conclude that the tubule is not attached to the shaft 

 and basal portion of the extruded nematocyst? 



CHAPMAN: No. That section did not show the hook hooked 

 on. It may never hook on. But it is suggestive. It's an interesting 

 arrangement. Why form a hook if you're not going to do something 

 with it? 



MUSCATINE: Isn't it possible that the hook results from a 

 tangential section through a twist in the tubule? 



CHAPMAN: If one examines the negative or a good print of 

 that particular figure very carefully, and specifically if one looks at 

 the membrane limiting that tubule, I think it would be conclud- 

 ed that the tubule had been cut very nearly sagittally and that it 

 probably is indeed a hook. It seems to have been fortuitously cut 

 precisely right. However, that is only an educated guess. 



HAND: Which end of the thread is that really on? 



CHAPMAN: It appears to be on the end that goes out first. 



CROWELL: After the thread is fully discharged, which end is 

 the hook on? 



CHAPMAN: It would be on the end which is farthest from the 

 stenotele. 



HAND: Then you are proposing that that hook does not evert? 



CHAPMAN: I am proposing that the tube which is coiled up 

 inside, which has a propeller-shaped cross section, may not evert. 



