18 Papers from the Marine Biological Laboratory at Tortttgas. 



is well illustrated in Veligers, Ctenophores, Trochophores, or Samper's 

 Actinian larva, and is due to the fact that the neuro-muscular system 

 is paralyzed by the magnesium and loses control of the cilia, which thus 

 revert to the primitive condition in Avhich they are not appreciably 

 influenced by the neuro-muscular system but each cilium is controlled 

 chiefly by its own cell. 



After cilia have ceased to beat in a magnesium solution they may 

 be restored to temporary activity by 0.625 molecular NaCl. In this case 

 ciliary movement is regained in the sodium chloride before the muscles 

 revive their activity, and the cilia cease to beat long before the muscles 

 cease to contract. The cilia cease to beat, or are dissolved, in from 4 to 8 

 minutes after being immersed in the sodium chloride, while the muscles 

 may continue to contract for half an hour or more. Often individual 

 ciliated cells are cast off from the epithelium and set free with their cilia 

 lashing vigorously, and if these freed cells be restored to sea-water they 

 continue to beat actively for hours in a normal manner, thus showing 

 that primitive cihated cells are practically independent of the neuro- 

 muscular system of the animal, and each cell contains within itself its 

 own means of maintaining its movement. 



EFFECTS OF POTASSIUM. 



It will be recollected that potassium in weak concentration is a 

 powerful but only momentary stimulant for neuro-muscular movements, 

 this initial activity being followed qtiickly by pronounced depression 

 and toxic effects. Upon cilia, however, its effects are the exact opposite. 

 Thus the movements of the cilia of the worm-trochophores, Veligers, and 

 Ctenophores are momentarily checked by a solution containing the 

 amounts and proportions of potassium and sodium found in sea-water,^ 

 but after a few seconds of arrested movement recovery takes place and 

 they beat slowly for about half an hour in the case of the Veligers or 

 worm larvae, and for about 4 hours in that of the Ctenophores. 



The muscular movements in all of these forms are at first highly 

 stimulated by this solution, but depression follows, so that the muscles 

 cease to move long before ciliary activity dies out. 



The movements of the cilia of the fresh-water Paramcecium are at 

 first checked by a weak concentration of potassium chloride or sulphate, 

 so that they cease to beat, or the animal reverses or spins in a circle. 

 Soon, however, recovery takes place and the Paramcecitmt swims slowly 

 but normally forward. Jennings ' first observed that Paramcecia placed 

 in a I per cent solution of potassium iodide at first swim backward, then 

 spin around on the short axis of the body for half an hour or more, and 

 finally recover and swim forward. 



Parker^ finds that 2.5KCI in 100 sea-water reverses the stroke of 

 the cilia of Metridium, and the same effect is produced by meat-juice, 

 but in this case probably not by the contained potassium, but by the 

 creatine in the meat. 



^ 0.625 molecular (looNaCl -f- 2.2KCI). 



^Jennings, 1899, Amer. Jour, of Physiol., vol. 2, p. 319. 



^ Parker, G. H., 1905, Amer. Jour. Physiol., vol. 14, p. 5. 



