NOTES ON THE BEHAVIOR OF GONIONEMUS. 



BT 



MAX MORSE. 



Perkins ('03), Yerkes ('02, '03 and '04), and others have 

 studied the behavior of Gonionemus murbachii (Ag.), the work 

 of Yerkes being most comprehensive and complete. Aside from 

 a general account of the habits, Perkins does not enter into the 

 responses of the medusa to the various external stimuli, such as 

 light, heat, etc. With respect to one conclusion reached by 

 Perkins, experiments of the writer point to a different interpreta- 

 tion. When a number of jelly-fish are placed in an aquarium, 

 they begin to swim directly upward to the surface. On reaching 

 the surface, the apex of the bell is pushed through the surface 

 film for perhaps three or four millimeters and immediately there 

 occurs an inversion of the bell and complete cessation of pulsation. 

 The medusa sinks passively downward with the oral portion 

 upward while the tentacles are thrown far out into the surrounding 

 medium. This process has been identified by Perkins as one of 

 "fishing," as by this means the tentacles bearing the stinging cells 

 come in contact with the prey and this is brought to the manu- 

 brium with readiness. 



The observations of the writer are as follows : A number of the 

 medusae were placed in a small glass vessel, a decimeter in diameter 

 and five centimeters in depth. Commercial olive oil was poured 

 on the surface of the water so that is was covered save in one place, 

 of about two centimeters diameter. The medusae began swim- 

 ming upward against the oil, but instead of inverting and sinking, 

 as in the case of pure w^ater, they continued swimming against it 

 until in some cases they became exhausted and sank, apex 

 upward, to the bottom of the vessel. Some of the medusae, as they 

 swam around the dish reached the portion of the surface left 

 uncovered by the oil. The result was an instantaneous inversion 

 of the bell foUow^ed by the cessation of all movements. 



A glass plate was lowered, in another case, below the surface of 



