Notes on the Physiology of Charybclen rastonii. 



histological findings obtained by previous 

 writers. 



To determine the course of nervous 



stimuli from the rhopalium the following 



experiments were tried. Three rhopalia 



were taken off and an incision was made 



starting from the bell edge and going 



upwards around the rhopalium niche as 



shown in the accompanying diagram (Fig. 



2). The medusa thus operated could swim 



about. Then the cut Avas extended farther 



Fig. 2. down, /. e., to a point a little above the 



velarium, pulsation stopped. This seems to show that the narrow 



area just above and along the velarium lacks the nerve plexus. 



From the experiments on pedalium reflex, which is to be de- 

 scribed in the next section, it will be seen that the nerve stimuli 

 do not reach the upper third of the bell. Although I have no know- 

 ledge of the distribution of nerve plexus in the Charybdea bell, yet 

 from these experiments it may be taken for warranted to conclude 

 that the bell is devoid of nerve plexus in the upper third of its 

 extent as well as near the velarium. 



m. Rhopalium-pedalium reflex. 



As was noted by Conant (Berger '00 p. 12 and p. 31) Charijh- 

 clea has an interesting reflex, which may be called the rhopalium- 

 pedahum reflex. It consists in this, that, if a rhopalium is lightly 

 stroked all the tentacles contract and all the pedalia are simul- 

 taneously bent into the bell cavity. Extraction of three rhopalia 

 does not make any difterence at all. Undoubtedly this reflex is 

 adaptive ; for the moment the enemy tries to seize the jellyfish 



