PULSATION WITHOUT MARGINAL SENSE-ORGANS. 



NaBr, but that a small amount of calcium or potassium added to the 

 Na solution will prevent the disk from pulsating. L/oeb concluded 

 that the calcium and potassium ions of the sea-water prevented the 

 center of the bell of Gonionemus from pulsating. This is untrue for 

 Cassiopea, for not only will the disk when deprived of sense-organs 

 pulsate regularly for more than an hour in an artificial sea-water 

 without calcium, but will also pulsate indefinitely in natural sea- 

 water, and will contract rhythmically in solutions containing NaCl + 

 KC1, or NaCl + CaCl 2 , or NaCl + KC1 + CaCl 2 in amounts and propor- 

 tions found in sea- water. All solutions containing magnesium tend 

 to prevent pulsation in the disk of Cassiopea. 



As a result of his work upon 

 the skeletal muscles in 1 899 Loeb 

 concludes that rhythmical con- 

 tractions occur only in solutions 

 of electrolytes, i. e., in com- 

 pounds capable of ionization, 

 and that in solutions of non-con- 

 ductors such as glycerin these 

 rhythmical contractions are im- 

 possible. However, Romanes 

 found that glycerin caused rhyth- 

 mical pulsation in Sarsia. 

 Greene (1898) and Howell(i9Oi, 

 p. 189) found that strips of heart 

 muscle, after having ceased to 

 pulsate in NaCl, will again pul- 

 sate if immersed in a pure solu- 

 tion of cane sugar or dextrose 

 isotonic with the NaCl solution, 



and I find that the heart 

 Salpa will pulsate normally for 



more than half-an-hour in dex- 



p . g 6 _ A disk o , ^^ pressed by a con _ 



of cen tric series of block-tin rings so as to insulate 



circuits of tissue. A disk so pressed may be 



caused to pulsate continuously. 

 trose, isotonic with sea-water (see table 6). Thus automatic beats 

 may occur in a solution entirely free from electrolytes, but, as How- 

 ell shows, these beats are probably dependent upon the presence of 

 electrolytes in the tissue itself. 



When we come to consider the effect of ions, etc., upon Cassiopea, it 

 will appear that one must be cautious of drawing general conclusions, 

 even from the most evident effects upon any one animal. Thus I find 

 that chemicals which produce certain perfectly definite and invariable 

 responses upon Cassiopea act differently upon Aurelia, Dactylometra, 



