CONCIvUSIONS NEW TO SCIENCE. 5 



The disk of Cassiopea usually pulsates spontaneously in an irregular 

 manner, immediately after the removal of its marginal sense-organs, 

 if it be placed in a solution containing NaCl, NaCl + KCl, NaCl + 

 CaClj, or NaCl + KCl + CaClj in the amounts and proportions found 

 in sea-water ; but it will not pulsate in any solution which contains 

 magnesium. 



7. The central disk of Cassiopea, if set into pulsation, will pulsate 

 longer than an hour in a solution resembling sea-water but lacking 

 calcium, whereas the normal perfect Medusa, or parts of the margin 

 containing sense-organs, cease to pulsate in this solution in less than 

 six minutes. The marginal sense-organs can not send forth stimuli 

 producing contractions unless they be consta7itly supplied with calcium 

 from the sea -water, whereas the sub-umbrella tissue of the disk itself 

 is relatively independent of the calcium of the sea- water. 



On the other hand, both the disk and the perfect Medusa will pul- 

 sate in sea- water saturated with CaSO^. 



8. The normal Cassiopea Medusa will pulsate fully three times as 

 long in a solution of NajSO^ containing the same amount of sodium 

 as is found in sea-water as it will in a solution of NagSOi isotonic 

 with sea-water. This indicates that the amount and proportion of 

 sodium in the sea-water is more important to pulsation than is its 

 osmotic property. 



9. The contractions of the heart of the loggerhead turtle are con- 

 ducted and maintained exclusively by the thin peripheral muscular 

 part of the wall of the heart, the thick cavernated tissue of the heart 

 being passive. Moreover, the outer muscular part of the heart's wall 

 is a better electrical conductor than is the cavernated tissue. A sim- 

 ilar condition is seen in Cassiopea, where the thin sub-umbrella tissue 

 of the disk is the only part which conducts and maintains the stim- 

 ulus for pulsation, and is a better electrical conductor than is the thick 

 gelatinous substance of the disk. 



10. The chief results of the paper are the discovery of a new method 

 of restoring pulsation in paralyzed Medusae, and also that magnesium 

 plays a most important role in restraining, controlling, and prolonging 

 pulsation in animal organisms. 



In Cassiopea the ectodermal, epithelial, or diffuse nervous elements 

 of the sub-umbrella transmit the stimulus which produces rhythmical 

 contraction. 



Rhythmical pulsation can be maintained only when a stimulus and 

 an inhibitor counteract one another, and cause the organism to be 

 upon the threshold of stimulation; thus permitting weak internal 

 stimuli to promote periodic contractions. 



