Effects of Temperature on Tropical Marine Animals. 13 



54.5 to 140, or 85.5 per minute, the kinetic energy in the same interval 

 having increased by 0.06. 



The equation for the rate of nerve-conduction at any temperature 

 between 17.5° C. and 35° C. may therefore be expressed by 



85j[-/ .73 + .7.5 + ^ \_ 1^ 

 0.06 L \ 273 + 17.5 / ^ ^-^^ 



or 



--[Pl^)-'J + - 



290.5 

 or, adopting general terms, 



= '*^4(^^')-']+^*-^- 



y = 



Wherein Ti is the absolute temperature of the lowest point of the series 

 and X is the temperature increment corresponding to the rate y, as has been 

 explained on page 1 1 . 



If we let I represent the rate of nerve-conduction and also the kinetic 

 energy of the solution at the lowest temperature of the series, then : 



The increase in rate 2.568 — i ^ 



; . = —^ = 26.13. 



The increase in energy 1.06 — i 



Thus the increment of increase in rate of nerve-conduction, for any 

 elevation in temperature between 17.5° and 35° C, is 26.13 times the incre- 

 ment of increase in kinetic energy of the solution. 



Hitherto we have been considering the rate at which the nerve-net 

 conducts the stimulus which produces muscular contraction. In nature 

 the stimuli which produce the nerve-impulse arise in the motor centers or 

 marginal sense-organs of the scyphomedusa and, as explained by Mayer, 

 1908, p. 119, the pulsation-waves annul themselves after each systole; 

 thus the rate of pulsation in the normal medusa is much lower than the rate 

 of nerve-conduction, being, indeed, determined solely by the rate at which 

 the motor centers can generate successive stimuli. In the paralyzed ring, 

 on the other hand, the rate of pulsation is simply that of nerve-conduction, 

 for no new stimuli are generated. 



The effect of temperature upon the perfect medusa is therefore its effect 

 upon the stimulus-generating ability of the motor centers — in other words 

 upon the rate of the metabolic process which produces stimulation. We 

 have, then, in Cassiopea a unique opportunity for differentiating between 

 the rates of production and that of the conduction of nervous impulses. 



Cassiopea xamachana with motor centers intact pulsates at its maximum 

 rate at about 33° C, ceasing to pulsate if cooled to 16.6" or if heated to 

 38.5". 



