208 The Mechanistic Conception of Life 



the surface, since they alone lend themselves to a statistical 

 comparison. In his account of the Valdivia expedition, Chun' 

 calls especial attention to this quantitative difference in the 

 surface fauna and flora of different regions. "In the icy water 

 of the Antarctic, the temperature of which is below 0° C, we 

 find an astonishingly rich animal and plant life. The same 

 condition with which we are familiar in the Arctic seas is 

 repeated here, namely, that the quantity of plankton material 

 exceeds that of the temperate and warm seas." And again, in 

 regard to the pelagic faima ui the region of the Kerguelen 

 Islands, he states: "The ocean is ahve with transparent jelly 

 fish, Ctenophores {Bolina and Callianira) and of Siphonophore 

 colonies of the genus Agalma." 



The paradoxical character of this general observation lies 

 in the fact that a low temperature retards development, and 

 hence should be expected to have the opposite effect from that 

 mentioned by Chun. Recent investigations have led to the 

 conclusion that life phenomena are affected by temperature in 

 the same sense as the velocity of chemical reactions. In the 

 case of the latter van't Hoff had shown that a decrease in 

 temperature by 10 degrees reduces their velocity to one-half 

 or less, and the same has been found for the influence of tempera- 

 ture on the velocity of physiological processes. Thus Snyder 

 and T. B. Robertson found that the rate of heart beat in the 

 tortoise and in Daphnia is reduced to about one-half if the 

 temperature is lowered 10° C, and Maxwell, Keith Lucas, and 

 Snyder found the same influence of temperature for the rate 

 with which an impulse travels in the nerve. Peter observed 

 that the rate of development in a sea-urchin's egg is reduced 

 to less than one-half if the temperature (within certain limits) 

 is reduced by 10 degrees. The same effect of temperature upon 

 the rate of development holds for the egg of the frog, as Cohen 

 and Peter calculated from the experiments of 0. Hertwig. 



1 Cllim, Aus den Tiefen des Weltmeeres, p. 225, Jena, 1903. 



