JELLYFISHES 



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the solution of sodium chloride and the other lobe is in 

 seawater, the rate of contraction quickly increases to 

 about three times what it formerly was. This shows that 

 the particular concentration of sodium chloride used, 0.62 

 molecular, was stimulating for the marginal body but not 

 for the nerve-net or the muscle. If a preparation that 



FIQ. 35. Diagram of a preparation of two muscle fields from Rhizostoma, one with an 

 attached marginal body and the other without such a body and so arranged that the two 

 fields may be partly immersed in vessels containing different solutions. Thus the sensitive- 

 ness of the marginal body may be compared with that of the rest of the neuromuacular 

 structure. (Based on the description by Bethe, 1909.) 



consists merely of nerve-net and muscle and that will not 

 respond to a 0.62 to 0.66 molecular solution of sodium 

 chloride, is now subjected to an 0.8 to full molecular so- 

 lution of the same salt, contractions will reappear for a 

 short time at least, showing that the combination of nerve- 

 net and muscle, though not so sensitive as the marginal 

 body, is nevertheless open to stimulation. 



When a preparation in which there is only nerve-net 

 and muscle is immersed in a sodium chloride solution, it 

 is claimed by Bethe that both the region in which there is 

 only nerve-net and that in which there is both nerve-net 

 and muscle become more open to stimulation and that of 

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