EFFECT OF INTENSITY OF TEMPERATURE 361 



To be brief, one must consider that, as anything but a rapid 

 response to the distribution of forces in the environment is incom- 

 patible with life, the animal capable of adapting itself to circum- 

 stances will live and propagate. Man, because of his highly 

 organised nervous and muscular systems, is able to adapt himself 

 readily and, therefore, reigns supreme. 



No case is known where acquired characters have been trans- 

 mitted to offspring. 



On the other hand the environment may have profound effects, 

 not in the nature of adaptation, but on the development of the 

 organism. 



Temperature. In ,Chap. XXXI. the effect of alterations in 

 temperature on physical, chemical and physiological phenomena 

 was considered. Temperature influences all life phenomena. 



(a) Development. One of the simplest experiments of this 

 nature is to determine the temperature coefficient of the develop- 

 ment of an egg. Usually the egg of the sea-urchin is chosen for 

 this purpose. Table LXVII. (Loeb and Chamberlain) gives the 

 time in minutes required from insemination to the first cell- 

 division for various temperatures. 



TABLE LXVII. 



EFFECT OF INCREASE OF TEMPERATURE ON CELL-DIVISION. 



Increase of temperature thus causes a more rapid development 

 of the egg. 



(b) Rate of Metabolism. Increase of temperature, within 

 limits, as we have seen, causes an increase in general metabolism. 

 More oxygen is used, more carbon dioxide is excreted, etc. Organs 

 work at a greater rate, e.g. the heart beats more rapidly. The 

 alterations of the rate of the heart of Fundulus (embryo) keeps 

 such regular pace with alterations in external temperature that 

 it could form the basis for a rough thermometer as Table LXVIII. 

 shows. From the figures we are also justified in inferring that the 

 influence of temperature in this reaction is a function of this 

 particular temperature and does not depend on whether the 

 organism is gaining or losing heat. 



