122 REPORTS ON INVESTIGATIONS AND PROJECTS. 



"the animal with the greater number of removed parts regenerates each part 

 more rapidly than the one with the lesser number of removed parts." 



The disk of Cassiopea is stimulated into temporary pulsation by all salts of 

 potassium, sodium, lithium, barium, and by iodine, weak acids, ammonia, and 

 glycerin. Loeb's contention that pulsation can not take place in a solution of 

 a nonconductor, such as glycerin, is not supported. 



Magnesium, calcium, and strontium salts do not stimulate the disk, and pro- 

 duce no contractions. 



The sodium chloride of the sea-water is the chief stimulant to pulsation in 

 Cassiopea, while magnesium is the chief restrainer of pulsation and counter- 

 acts the influence of the sodium chloride. Thus, Cassiopea will pulsate in a 

 pure % normal NaCl solution for half an hour, but comes to rest in less than 

 2 minutes in a solution containing the amounts and proportions of NaCl and 

 magnesium found in sea-water. 



The calcium of the sea-water assists the NaCl to resist the retarding effects 

 of magnesium. Thus, Cassiopea will pulsate longer than an hour in a solu- 

 tion containing the amounts and proportions of NaCl, magnesium, and calcium 

 found in sea-water; but ceases to pulsate in less than 2 minutes in a solution 

 containing only the NaCl and magnesium. 



Unlike calcium, potassium does not assist the NaCl to overcome the stupe- 

 fying influence of the magnesium. Thus, Cassiopea ceases to pulsate almost 

 as quickly in a solution containing the NaCl, magnesium, and potassium of 

 sea-water, as it does in a solution containing only the NaCl and magnesium. 



The potassium of the sea-water serves to stimulate pulsation in connection 

 with both calcium and NaCl. Thus, Cassiopea pulsates only temporarily 

 and with about a normal rate in NaCl-f-KoSOi or NaCl+CaS04, whereas 

 it pulsates continuously and at fully twice its normal rate in NaCl-f- K-SOi-f- 

 CaSCX. 



We see then that the NaCl. K, and Ca of the sea-water unite in stimulating 

 pulsation and resisting the stupefying effect of the Mg. All together they pro- 

 duce an indifferent fluid which neither stimulates nor stupefies the disk of 

 Cassiopea. The explanation is quite different from that of Loeb in his account 

 of the pulsation of 'Gonionemus. 



The sea-water is an indifferent fluid for the disk of Cassiopea, and it does 

 not pulsate when its marginal sense-organs are removed, simply because 

 the sea-water does not stimulate it. If stimulated in sea-water, in any man- 

 ner, it pulsates readily. This is also true of Gonionemus, and Loeb's state- 

 ment that the K and Ca of sea-water inhibit pulsation is not supported ; for 

 the center of Gonionemus will pulsate actively in sea-water whenever it is 

 touched by a solution of potassium salt, or otherwise stimulated. It does 

 not pulsate ordinarily in sea-water simply because the sea-water does not 

 stimulate it. 



On the other hand, the disks of Aurelia and Dactylometra pulsate in sea- 

 water as soon as they recover from the shock of the operation resulting in 

 the loss of their marginal sense-organs. Unlike Cassiopea and Gonionemus, 

 both Aurelia and Dactylometra are weakly stimulated into pulsation by 

 magnesium, and thus the sea-water as a whole weakly stimulates them, pro- 

 ducing irregular but sustained pulsations. 



The central disk of Cassiopea will pulsate longer than an hour in a solu- 

 tion resembling sea-water but lacking calcium, whereas the normal perfect 



