236 THE LESSON OF EVOLUTION 



abiogenesis with his usual clearness. He says" 

 organic substance may, perhaps, originate now ; but 

 more probably it originated at the time when the heat 

 of the surface of the earth was falling through the 

 range of temperature at which the higher organic 

 compounds are unstable. Organic matter, he 

 thinks, was not produced at once, but was reached 

 by steps. Inferior types of organic substance, by 

 their mutual actions under fit conditions, evolved the 

 superior types, ending in organisable protoplasm. 

 " And to the mutual influence of its metamorphic 

 forms under favouring conditions, we may ascribe 

 the production of the still more composite, still more 

 sensitive, still more variously-changeable portions of 

 organic matter, which, in masses more minute and 

 simpler than existing Protozoa, displayed actions 

 verging little by little into those called vital ; actions 

 which protein itself exhibits in a certain degree, and 

 which the lowest known living things exhibit only 

 in a greater degree." (1. c. p. 700). 



This idea of the gradual complexity in the growth 

 of carbon compounds is a possible one, for we see the 

 same thing in the process of assimilation by living 

 protoplasm. But, as chemists have not yet been able 

 to follow it, we must hold it as a speculation only. 

 There can be no difficulty in reproducing in the 

 laboratory all the conditions mentioned by Mr. 

 Spencer, but, up to the present, albumen or protein 

 have evaded the efforts of experimentalists. It must 

 be remembered, not only that protoplasm is killed by 

 a temperature far less than that at which the pro- 



"" Principles of Biology," 2nd edition, vol. 1, p. 698. 



