16 Papers from the Marine Biological Laboratory at Tortugas. 



the ciliary movements are most seriously depressed in NaCl the neuro- 

 muscular system is highly stimulated, and long after ciliary activity 

 has ceased the muscles continue to contract and move actively. 



Thus a solution of 5 grams of Na 2 C 2 O 4 in 1000 c.c. of sea-water is a 

 stimulant for neuro-muscular movements, but it is a primary depressant 

 for ciliary activity. A similar statement may be made of the effects of 

 NaOH in sea-water. 



After ciliary movement has ceased in 0.6 molecular sodium chloride 

 solution, activity may be revived by placing the animals in isotonic 

 magnesium solutions such as molecular MgSO 4 or 0.4 molecular MgCl 2 ; 

 provided the cilia have not already dissolved in the sodium solution. 

 When so revived by magnesium the cilia beat incessantly at a rapid rate 

 while the muscles subside into quiescence. 



EFFECTS OF MAGNESIUM. 



Magnesium is the most powerful depressant among ions of blood- 

 salts for the neuro-muscular system, but among these salts it is the most 

 efficient single ion for maintaining ciliary movements. Its effects are 

 thus the exact opposite of those of sodium. For example, the cilia of 

 the trochophore larva of the palolo worm continue to beat for nearly an 

 hour in pure 0.4 molecular MgCl 2 , whereas such a solution causes muscu- 

 lar activity to cease in a few minutes. In 0.625 molecular (looNaCl-f 

 n.6MgCl 2 ) the trochophores of the palolo and Spirobranchus soon begin 

 to circle, as shown in fig. 5. At the end of about half an hour, however, 

 they recover from this circling and move forward slowly, but in a normal 

 manner. Some of them cease to move at the end of an hour, but a few 

 continue to vibrate their cilia for from 3 to 7 hours, after which they die. 



In the Ctenophore Bolinopsis vitrea the muscles are relaxed and the 

 cilia are highly stimulated in magnesium, so that the animal darts with 

 abnormal rapidity through the water, but the stroke of the cilia is 

 reversed and the coordination destroyed, so that the creature moves 

 backward (mouth forward) sometimes for more than 45 minutes. 



Fresh-water infusoria, such as Paramacium, soon cease to move 

 their cilia in 0.166 molecular NaCl, but remain active a very much longer 

 time in an isotonic solution of MgCl 2 or MgS0 4 , although their rate is 

 never as fast as the normal in these solutions. 



Spermatozoa of terrestrial vertebrates cease to move almost in- 

 stantly in NaCl, but will continue to move for more than an hour in 

 MgCl 2 . In the worm larvae, Veligers, Actinians, and Ctenophorae it is 

 noticeable that the cilia continue to beat in magnesium long after mus- 

 cular activity has ceased. 



The addition of potassium or calcium to solutions composed of 

 sodium and magnesium greatly prolongs their power to sustain ciliary 

 movement. Thus in 0.625 molecular (iooNaCl + n.6MgS0 4 + 2.2KCl) 

 cilia of the trochophores of the palolo and Spirobranchus cease at once 

 to beat, but in a few seconds they recover and the larvae swim for from 18 

 to 48 hours at a rate nearly if not quite normal, reacting normally to 

 light. This behavior is remarkable in contrast with that of neuro- 

 muscular movements in the same solution, for in this solution Cassiopea 



