Mast, Loeb's Mechanistic Conception of Life. 591 



Loeb says (p. 207): "It has of fen been noticed by explorers 

 who have had a chance to compare the faunas in different climates 

 that in the polar seas such species as thrive at all in those regions 

 occur, as a rule, in much greater density than they do in moderate 

 or warmer regions of the ocean." He holds that the results of a 

 number of investigators show that it requires an increase of about 

 10 in temperature to double the rate of development in organisms, but 

 maintains (p. 209) that the length of life of sea-urchin eggs (fertilised 

 and unfertilised) is doubled if the temperature is decreased only 1 . 

 And he says: "Lowering the temperature by 10 degrees therefore 

 prolongs the life of the organism 2 10 , i. e., over a thousand times, 

 and a lowering by 20 degrees prolongs it about one million times. 

 Since this prolongation of life is far in excess of the retardation 

 of development through a lowering of temperature, it is obvious 

 that, in spite of the retardation of development in Arctic seas, 

 animal life must be denser there than in temperate or tropical seas." 



If there is anything in this theory we should expect in the 

 temperate zone that pelagic life would be much more abundant in 

 winter than in summer. We should expect our ponds to swarm 

 with microorganisms when they are covered with ice. Of course 

 every one knows that this is not true. 



In this instance we have an illustration of a peculiar method 

 of reasoning not rarely found in Loeb's works. He finds that a 

 change of 1 degree at a given temperature produces a given effect 

 on a sea-urchin egg and concludes that a change of 1 degree will 

 produce the same effect in practically all organisms over a wide 

 range of temperatures. 



Another illustration of the same tendency to excessive generaliza- 

 tion is found in the following statement (p. 45): "Every animal is 

 continually producing acids in its cells, especially carbonic acid and 

 lactic acid; and such acids increase the tendency in certain animals 

 to react heliotropically . . . Fluctuations in the rate of the produc- 

 tion of these substances will also produce fluctuations in the 

 heliotropic sensitiveness of the animals. If, for instance, the active 

 mass of the photosensitive substance in a copepod is a relatively 

 small, a temporary increase in the production of carbonic acid can 

 increase the photosensitiveness of the animal sufficiently to cause 

 it to move for the period of a few seconds directly toward the 

 source of light. Later the production of carbonic acid decreases 

 and the animal again becomes indifferent to light and can move 

 in any direction. Then the production of carbonic acid increases 

 again and the animal goes again, for a short time, toward the 

 light." Thus it is clear that our author holds that variability in 

 the response of animals to light is due to variability in the pro- 

 duction of acids within them. Superficially this appears to be a 



