2 888.] Evolution as illustrated by the Geogr. Distrib. of Plants. 291 



These words seem to be only consistent with the well-known 

 theological doctrine of " economy of miracles " and one would be 

 inclined to conclude from them that Darwin consiiered that origin of 

 organic life on the earth was supernatural. 



The mere fact moreover of Darwin tracing back all organic life to 

 one or at the most a dozen primordial progenitors seems inconsistent 

 with any hypothesis but that of his believing in the supernatural 

 origin of life. If life originated from inorganic matter according to a 

 natural law it is quite incredible that this law in all earthly time and 

 space should have operated only once or even at most a dozen times. 

 Assuming then that Darwin regarded the origin of organic life on 

 the earth as supernatural, it is obviously in vain to look to his views 

 in this respect for any light it may throw on the origin of species. 



But though Darwin's views cannot assist us in this respect, it may 

 be of some use to consider the subject on its own merits. 



Setting aside the theory of supernatural origin of life, not as being 

 untrue or improbable but as putting the question out of the reach of 

 scientific enquiry, there are three other hypotheses on this subject 

 which seem worth consideration: 



(1.) Organic life always existed on the earth. 

 (2.) Organic life came to the earth by migration. 

 (3.) Organic life originated and perhaps still continues to originate 

 •:. according to some natural law. 



-Let us consider each of these hypotheses in turn. 



(2.) Organic Life always existed on the Earth. 



Against the first hypothesis it may be urged : 



I. The perpetual existence of life on the Earth is inconceivable 

 Everything must have had a beginning, therefore organic life on the 

 Earth must have had a begi nixing. 



II. The perpetual existence of organic life on the Earth is incon- 

 sistent with La Place's theory of the origin of our planetary system, 

 according to which theory the Earth must at one time have been 

 in a physical eondition inconsistent with the existence of organic life 

 in any form known to us or from which it is at all probable that 



, existing life would have been derived. 



JI. To the first of these objections the reply is that the word 

 inconceivable is here misused. No doubt the forms of things as we 

 observe them are always changing, and In this sense we are con- 

 strained to believe that all that exists is transitory. On the other 

 hand, however, we are equally constrained to belieye in the continuity 



