152 REPORTS OF INVESTIGATIONS AND PROJECTS. 



Prof. Charles Zeleny studied the regeneration of the chelae of the gulf- 

 weed crab (Portumis sayi) and found that there is no change in the power 

 of regeneration as a result of successive removal of the chelae, and also 

 that there is no appreciable change in the left chela as a result of the removal 

 and regeneration of the right chela. He also studied regeneration in the 

 medusa Cassiopea and discovered that the rate of regeneration is independent 

 of the functional activity or inactivity of the medusa. This result was sub- 

 stantiated by the later work of Stockard. In some other respects Stockard's 

 conclusions are in conflict with those of Zeleny, although their observations 

 are essentially in accord one with another. 



Among other researches carried out at Tortugas mention may be made of 

 the work of the Director, who finds that in sea-water the sodium ion stimu- 

 lates, while mangesium. calcium, and potassium tend to retard neuro-mus- 

 cular activity in marine animals. The sea-w^ater is thus a balanced fluid, the 

 stimulating influence of the Na being offset by the inhibiting eft'ect of Mg, 

 Ca, and K. Pulsations or other muscular movements of marine animals are 

 thus due to internal stimuli. In the case of the scyphomedusae the stimulus 

 which produces pulsation is due to the constant formation of NaoC204 in the 

 sense-clubs, and this precipitates the Ca of the CaCL of the sea-water form- 

 ing the CaCo04 crystals of the sense-club and setting free NaCl, which acts 

 as a nervous and muscular stimulant ; and indeed sodium may be the natural 

 stimulant for the production of movements in all marine animals. 



The Director also discovered that the cilia of marine animals are affected 

 by the cations of the sea-water in a manner the exact converse of the muscles. 

 Thus sodium is the most powerful stimulant for nerves and muscles, but the 

 most potent inhibitor of ciliary movement. Also magnesium is the most 

 powerful inhibitor in the sea-water for the neuro-muscular system, but the 

 most active stimulant for cilia. Similarly, weak solutions of potassium at 

 first stimulate, later retard the neuro-muscular system, but they first retard 

 and later stimulate cilia. Strong solutions of potassium at once inhibit 

 muscles but temporarily stimulate cilia. Calcium weakly inhibits muscles 

 and stimulates cilia. 



Thus for the neuro-muscular system, we have the stimulating effect of Xa 

 offset by the stupefying influence of Mg, K, and Ca ; whereas upon animal 

 cilia the stupefying influence of Na is offset by the stimulating influence of 

 Mg, K, and Ca. 



Moreover, certain bacteria living in fresh-water react to these ions as do 

 the cilia of animals, and this inclines one to suppose that the ciliary move- 

 ment of animals may have been taken over directly from plant-like ancestors, 

 and that neuro-muscular movements were developed later, and in a converse 

 manner. 



