38 PUIvSATlON OF 



other salt this was made isotonic with the NaCl of sea-water. The 

 potassium was so introduced as always to give the same amount of the 

 element (K) as is found in sea- water. 



TABLE 3. How calcium revives rhythmical pulsation in Cassiopea after all 

 movement has ceased in solutions contaiuing Na or Li, isotonic -with the NaCl 

 of sea-zuater, and potassium in the same amount as is found in sea-zvater. 



Normal M e d u s ae 

 taken from sea- 

 water and placed 

 in 



They ceased to pulsate in 



Were restored to pulsation by 

 the addition of any of the 

 following calcium salts, tried 

 separately. 



NaCl + KC1 . . . 

 NaCl + K 2 S0 4 . 



NaCl + KClO 3 



Na 2 C03+K2C0 3 ... 



I4O+KC1. 



About 120 minutes 



20 to 30 minutes. Very rapid pulsation 



at first, followed by periods of rest and 



activity. 

 12 to 18 minutes. Pulsation not so rapid 



as in NaCl + K 2 SO 4 

 4 to 10 minutes. Pulsation not very 



rapid at first. Slower than in NaCl + 



K 2 C0 3 

 3 to 7 minutes. Pulsation slow and 



weak. 

 Less than i minute. Pulsation rapid at 



first. 



i to 6 minutes. Pulsated slowly at first. 



CaCl 2 , CaSO 4 . 



CaS0 4) CaCO 3 , CaCl 2 ,or CaH 2 O 2 . 



Very active pulsation restor- 

 ed by CaSO4,CaCl 2 ,orCaH 2 O 2 . 

 CaSO 4) CaCls, or CaH 2 O 2 . 



CaCO 3 revived weakly. 



CaCla or CaH 2 O 2 . Some of the 

 Medusae did not revive pul- 

 sation. 



CaCl 2 . All three Medusae 

 revived weakly. 



Table 3 shows that Cassiopea pulsates longer and more rapidly in 

 a solution of NaCl + KC1 than in any other solution named in the 

 above table. Also, sodium and potassium nitrates are more injurious 

 than a solution in which the sodium is replaced by an isotonic amount 

 of lithium. Evidently the anions as well as the cations of the salts 

 have a decided influence upon the rhythmical movement. This is 

 also shown by the fact that Medusae pulsate longer and with greater 

 regularity of movement in NaCl + K 2 SO 4 + CaSO 4 + CaCO 3 than 

 they do if we omit the CaCO 3 and replace it by an equivalent amount 

 of CaSO 4 . It will be recalled that Rogers (1905, p. 249) found that 

 the addition of small amounts of Na 2 CO 3 or NaOH to solutions 

 have a beneficial effect in maintaining the rhythm of the crab's heart, 

 and he attributes this effect to the neutralization of small amounts 

 of free acid in the solutions. Ammonia, KOH, or NaOH in small 

 amounts have, however, little effect upon the rhythm of Cassiopea, 

 but if the sea- water be rendered almost neutral by HC1 (it is nor- 

 mally decidedly alkaline at Tortugas) the pulsations of the Medusae 

 lose energy, and finally the rate declines, and movements, although 

 regular, are feeble and slow. Thus the rates of three Medusae declined 

 in six hours from 37-50 to 13-17 per minute, due to the effect of a 

 minute quantity of HC1 in the sea-water, causing it to become almost 

 neutral, but still alkaline to litmus test. It seems improbable, how- 



