SOME UNSOLVED PROBLEMS IN GEOLOGY. 61 



preceding attempt to estimate them makes sufficiently manifest, and to 

 arrive at no more definite conclusion than was long ago arrived at by 

 Pliny, that " vita arborum quarundam immensa credi potest " (" The 

 life of some trees may be believed to be prodigious "). Longman's 

 Magazine. 



SOME UNSOLVED PEOBLEMS IN GEOLOGY.* 



By Db. J. W. DAWSON. 



II. 



AGAIN" : we are now prepared to say that the struggle for existence, 

 however plausible as a theory, when put before us in connection 

 with the productiveness of animals, and the few survivors of their multi- 

 tudinous progeny, has not been the determining cause of the introduc- 

 tion of new species. The periods of rapid introduction of new forms 

 of marine life were not periods of struggle, but of expansion those 

 periods in which the submergence of continents afforded new and 

 large space for their extension and comfortable subsistence. In like 

 manner it was continental emergence that afforded the opportunity 

 for the introduction of land animals and plants. Further, in connec- 

 tion with this, it is now an established conclusion that the great 

 aggressive faunas and floras of the continent have originated in the 

 north, some of them within the Arctic Circle ; and this in periods of 

 exceptional warmth, when the perpetual summer sunshine of the Arctic 

 regions co-existed with a warm temperature. The testimony of the 

 rocks thus is, that not struggle, but expansion, furnished the requisite 

 conditions for new forms of life, and that the periods of struggle 

 were characterized by depauperation and extinction. 



But we are sometimes told that organisms are merely mechanical, 

 and that the discussions respecting their origin have no significance, 

 any more than if they related to rocks or crystals, because they relate 

 merely to the organism considered as a machine, and not to that which 

 may be supposed to be more important, namely, the great determin- 

 ing power of mind and will. That this is a mere evasion, by which 

 we really gain nothing, will appear from a characteristic extract of an 

 article by an eminent biologist, in the new edition of the " Encyclo- 

 paedia Britannica " a publication which, I am sorry to say, instead of 

 its proper role as a repertory of facts, has become a strong partisan, 

 stating extreme and unproved speculations as if they were conclusions 

 of science. The statement referred to is as follows : " A mass of 

 living protoplasm is simply a molecular machine of great complexity, 

 the total results of the working of which, or its vital phenomena, 



* Address of the President of the American Association for the Advancement of Sci- 

 ence, delivered at Minneapolis, August 15, 1883. Reprinted from "Science." 



