Converse Relation between Ciliary and N euro-Muscular Movements. 9 



Figure 3 gives a graphic illustration of the effects of various solu- 

 tions containing from one to three of the four constituent cations of 

 van't Hoff's sea-water 1 on Lepas (left-hand column), Cassiopea (middle), 

 and Annelid worms (right-hand column). The drawings of Lepas and 

 of the Annelids are from careful sketches made from actual cases and 

 are quite true to nature, but those of the Scyphomedusa Cassiopea are 

 wholly diagrammatic, for the mouth-arms are not shown and the flatten- 



Na 



Na 



Na 



Na 



-f IVIg 



Ncl 



Na 



Na+Ca 



Na + Ca 



Na+Mj+Ca 



Na + Mj 



Na + 



FIG. 3. 



ing of the bell in magnesium is much exaggerated in order to make it 

 more apparent. 



The figures show that muscular relaxation is produced in solutions 

 containing magnesium, and tetanus in solutions containing calcium; 

 also that calcium and magnesium counteract each the other in these 

 respects when both are present in a solution containing sodium. Potas- 

 sium, on the other hand, has but little power to alter the effects of calcium 

 or magnesium. For example, in 0.625 molecular (looNaCl + 7.8MgCl 2 

 + 3-8MgSO 4 ) Lepas comes to rest without initial stimulation in about 

 half an hour, with its pedicel abnormally extended and its branchial 



1 The complete formula is 0.625 molecular (looNaCl + 7.8MgCl 2 + 3.8MgSO 4 

 + 2.2KC1 + 2.sCaCl 2 ). 



