3^6 Death and Dissolution of the Organism 



may account at least partly for the fact that in tropical 

 seas the pelagic fauna is so much more limited than in 

 polar seas.^ It is quite probable that the high tern- 

 perature coefficients at the utmost limits are only an 

 expression of the coagulation time of certain proteins. 

 P. and N. Rau state that in the cold certain butter- 

 flies live longer, and similar statements exist for the 

 silkworm, but these statements are not based on exact 

 experiments, which are difficult. Dr. Northrop and 

 the writer have started experiments on the influence 

 of temperature on the duration of life of the fly Droso- 

 phila. Newly hatched flies were kept first without 

 food except water and air at 34°, 28°, 24°, 19°, 14*^, 

 and 10°; and second with cane sugar. The average 

 duration of life was as follows: 



With water days With cane sugar days 



34° 2.1 6.2 



28° 2.4 7.2 



24° 2.4 9-4 



19° 4.1 .12.3 



14° 8.3 



10° 11.9 



' K. Brandt ("tJber den Nitratgehalt des Ozeanwassers und seine 

 biologische Bedeutung," Abh. d. kais. Leap. Carol, deutsch. Akad. d. 

 Naturfoscher., 19 15) accounts for this fact by the assumption that through 

 the greater activity of the denitrifying bacteria in the tropical waters 

 the amount of available nitrates is here comparatively smaller than 

 in the polar oceans. The writer fully appreciates the importance of this 

 fact but nevertheless is inclined also to see a limiting factor in the 

 enormously rapid decline of the duration of life at the upper temperature 

 limits. 



