1888.] Evolution as illustrated by the Geogr. Distrib. of Plants. 293- 



to size bj the perceptions of our senses, even though aided by instru- 

 ments a million times more powerful than the best devised by man. 

 It is as well to remember that the abysses of the infinitely little are 

 really as profound as those of the infinitely great, that if our tele- 

 scopes reveal to us ever-increasing profoundities of distance, our 

 microscopes equally reveal to us the profoundities of minuteness, and 

 in neither direction do we find trace nor can we conceive any 

 possibility of limit. 



IT. The migrationary hypothesis may likewise be objected to on^ 

 the ground that it merely removes the problem as to the origin of 

 organic forms to some other time and place. This is true, but the 

 hypothesis of the co-eternal existence of organic and inorganic forms 

 in the universe as a whole does seem to present fewer difficulties than, 

 their co-eternal existence on the Earth. 



Moreover we are not now concerned with the relative probability of 

 the various hypotheses as to the origin of organic life, but with the 

 light which these hypotheses respectively throw on the theory of 

 subjective tendency to variation. Whether the migrationary hypo- 

 thesis is or is not satisfactory as to the origin of life, all we are 

 concerned about is whether this hypothesis supposes the introduction 

 of life on the earth in one or only a few cases, or in an indefinite 

 number of cases, and it can hardly be denied that the latter is the 

 «ase. 



(<?.) Organic Life originated and perhaps still originates from Inorganic 

 Life according to some Natural I^aiv of Continuity. 



This hypothesis, sometimes called that of Spontaneous Generation > 

 is summarily rejected by some as being inconceivable. Here again 

 the word inconceivable is wrongly used. There can be no difficulty 

 in the conception of continuity between what is called the organic 

 and the inorganic forms of matter, though there may be some 

 difficulty in believing that such continuity actually exists, snice all 

 our experience goes to shew that organic forms invariably proceed, 

 from previously existing organic forms. This difficulty would, how- 

 ever, be somewhat diminished by the reflection that our experience 

 imperfectly covers only an infinitesimal part of nature. Because 

 physicists have not yet consciously succeeded in producing organic 

 from inorganic forms in the glass bottles of their laboratories, it 

 by no means follows that in the wonderfully diversified conditions 

 '^hich exist and have existed on the Earth, such production is 



