DEPARTMENT OF MARINE BIOLOGY. 217 



From the quantitative determinations, the follo"\ving conclusions have been 

 reached : 



1. The rate of CO2 production in the ganglia of the Tortugas Lirnulus 



at 27° C. is slower than that of the northern forms at 23° C. 



2. In both regions, a male is usually smaller in size than a female. It 



was previously noted in the northern forms that the rate of CO2 

 production in the ganglia of the male was considerably higher than 

 that in the female. A similar difference was discovered to exist in 

 the ganglia of the two sexes at Tortugas. Whether this difference 

 was due to the differences of age, sex, or mere size of cord was not 

 determined. 



3. This difference in metabolic activity of the two sexes is, however, only 



true at normal temperatures. At 33° the ganglia from both sexes give 

 about the same amounts of CO2 for a gram of the tissue. In other 

 words, the temperature coefficient of CO2 production in the ganglia 

 of the female heart is lower than that of the male from 27° to 33° C. 



4. A similar difference was observed in the claw nerve of the same animal 



at Tortugas. 



5. By comparing the observations made at Woods Hole with those made 



at Tortugas, I came to the following conclusions: The tropical 

 animal can live near the death-point, not because it can maintain a 

 higher rate of metabolism, but rather because of differences in the 

 protoplasm which produce a relatively low rate of metabolism in 

 high temperatures. This conclusion is further supported by the 

 behavior of the tropical Liviulus, which, to all appearances, does not 

 exhibit any greater muscular activity than does the northern form, 

 although if it had a greater rate of metabolism in the tropics greater 

 muscular activity might be expected. This conclusion is merely 

 a suggestion, however, and should be further tested upon other forms 

 as well as upon other tissues before we draw a general conclusion. 



6. Although there seems to exist a certain relation between heat paralj^sis, 



death temperature, and general tissue metabolism, we can not yet 

 say what determines death temperature. It would be very inter- 

 esting to measure the metabolic activities of the ganglia in the 

 neighborhood of the higher and lower death-points in both regions, 

 an experiment which was not practicable with the biometer with- 

 out some modifications. 



II. Temperature Coefficient of Metabolism in the Nerve Fiber. 



In recent years it has been pointed out by many that magnitude and varia- 

 tion of the temperature coefficient of physiological activities does not neces- 

 sarily tell us what kinds of reactions are involved. This argument has been 

 against the view that the relatively high temperature coefficient of the 

 velocity of nerve impulse suggests that the nerve impulse is of a chemical nature. 



Since it has been demonstrated that the resting nerve fiber gives off CO2, 

 and, on stimulation, its CO2 production is increased, the direct determination 

 of a chemical change in the nerve fiber under various temperatures was very 

 desirable. 



Although the present form of the biometer is such that it can not be used 

 satisfactorily for large variations at high temperatures, it could easily be used 

 to determine the amounts of CO2 produced at various temperatures between 

 27° and 33°, which are the natural temperature changes at Tortugas. 



From various quantitative determinations, it was shown that the amount 

 of CO2 produced by the claw nerve of Limulus at 27° without stimulation is 



