SOYPHOMEDUSAE COLLECTED BY STEAMER " ALBATROSS." 179 



as great as that of the electrical conductivity of the sea water, and 

 this suggests that the sodium-calcium- ion proteid may have a high 

 temperature coefficient of ionization ; for if the rate of nerve conduc- 

 tion is proportional to the concentration of the reacting cations, this 

 would account for the high temperature coefficient of the rate of 

 nerve conduction. 



Also the sodium-calcium-ion proteid is probably colloidal in char- 

 acter and being in an alkaline medium it is doubtless negative elec- 

 trically. Thus, under the influence of the decided negative potential 

 which accompanies the reaction of nerve conduction, the surface 

 tension on the particles of this colloid must be augmented and this 

 may reduce the size of the particles in the manner stated by Mayer, 

 Schaeffer, and Terroine, 1907. 



Granted this were the case, the solubility of the particles would be 

 augmented; for the surface decreases only as the square, while the 

 volume declines as the cube of the radius. Thus more ions of sodium 

 and calcium would pass into solution in a given time from the many 

 small than from the few large particles ; the mass remaining constant. 



Nerve conduction is therefore probably a very complex chemical 

 reaction, in which also an enzyme action may possibly be involved as 

 postulated by Harvey, 1911. 



Goldfarb showed that Cassiopea regenerates more rapidly in 90 

 per cent of sea water (90 parts of sea water mixed with 10 parts of 

 distilled water) than it does in normal sea water. Nerve condition 

 is, however, most rapid in slightly concentrated sea water. 



In all Scyphomedusae, excepting the Ehizostomae, tentacles are 

 found at the bell-margin, and usually grow out from between the 

 notches of the rim. These tentacles are hollow, the stomach cavity 

 being continued into them as it is also into the sense-clubs; indeed, 

 the sense organs are only highly modified tentacles. 



Powerfully developed circular, or a combination of circular and 

 radial, muscles are found in the under, concave part of the umbrella 

 (the subumbrella), and here also there is a network of nerve fibers 

 connecting the muscles with the sense clubs. Curiously, there are no 

 muscles, and probably no nerves, over the outer convex part of the 

 umbrella (the exumbrella). 



Those who have handled jellyfishes know that they are capable of 

 inflicting a sharp sting, the tentacles being especially active in this 

 respect. Closely clustered over the surface of the tentacles and other 

 parts of the jellyfish there are minute cells, each containing a hollow 

 tube coiled rope-like within the cell. Upon excitation these little 

 tubes are turned inside out and shot forward, and being more or 

 less barbed they penertate the skin, causing a sharp sting due in part, 

 it appears, to formic acid. Thus it is that these large jellyfishes are 



