-71- 



Moore (1920) states that if suspended with the ventral side 

 down, an Aateriae forbesi -will remain motionless in a state of 

 ventral flexure indefinitely. This while not absolutely tru of an 

 active Pisaater especially at first, and very far from tjue of an 

 active Pyono podia, may be said to describe the behavior of th more 

 inactive specimens that I h>ve tried the experiment upon. Moore 

 says, furthermore, that if the dorsal wall of a ray of such a sus- 

 pended specimen be irritated by rubbing it with a glass rod, the 

 ray will flex dor sally. I have confirmed this. Moore, however, 

 neglects to mention a fact, first observed by Romanes and Swart (1881) 

 that the tube feet of such a ray whose dorsal dermis is irritated 

 increase in activity. The normal orientation of tube feet on an 

 active but unoriented speoiraan is toward the tip of the ray. It would 

 seem then that the dorsal flexure is due to the principle that a ray 

 tends to set itself more nearly at right angles to the actively or- 

 iented tube feet* This is perhaps the more acceptable as a point 

 of view since the activity of the tube feet has been observed to 

 spread to the tube feet of other rays and to be followed by dorsal 

 movements or lateral twistings of these other rays. 



Moore comes to the conclusion from these and similar ex- 

 periments that the dorsal flexures of the rays which he has 



' 

 elicited by contact stimulations are the separate parts of the 



righting reaction. Aside from the fact that the righting reaction 

 has been observed to start without any contact stimulation of the 

 rays, my observations and the statements available in the literature 

 have led me to the conclusion that lateral twistings of the rays 

 are muoh more important in the righting reaction (save that of 

 otsn) than are me^e dorsal flexures. 



Evidence from the persistence ojf ffle ** uni f i ed iflipul s e " 



