The Philosophy of Evolution. 49" 



between any two sets in the series expresses the idea of the 

 Creator, and this must be constant. Completing the series as 

 indicated by different plants, we may assume that if any term 

 is apparently wanting, it is only because it has not been dis- 

 covered. In neither of these cases would it be asserted that 

 any physical evolution had taken place — the terms form a 

 series of which each term is equally determined by the opera- 

 tion of a fixed law ; and yet it is an operation precisely analo- 

 gous to that which in the case of animals presents every ap- 

 pearance of a real evolution. Take, for instance, a series of 

 animals, presenting at one period of time the simplest and most 

 rudimentary forms, and at another the most complex and 

 highly organized ; we cannot do otherwise than conceive these 

 two extremes as related by intermediate terms, through the 

 operation of some law which holds good throughout the series. 

 The relation subsisting between any two, must be the same as 

 that subsisting between any other two similarly situated, or a 

 departure from that relation which is itself governed by a def- 

 inite law discoverable from a comparison of two sets of terms. 

 The' application of this law is so universal and so rigid that we 

 need not hesitate to interpolate a missing term, and confidently 

 assert that it either does exist or has existed. To deny this 

 principle is to deny the necessity of continuity in reasoning. 

 This continuity of thought is represented in matter by the per- 

 sistence of generic forms under specific differences. But just 

 as the specific is the generic with certain additions, so the in- 

 dividual is this same generic with still further additions ; and 

 these additions, whether considered solely in space, as given in 

 the symbols of physical science, or in time as in the concep- 

 tions of intellectual science, must be determined by the same 

 unvarying law. The persistence of the same form furnishes 

 us the means of identifying this relation, while the differences 

 reveal to us the successive steps by which the generic was dif- 

 ferentiated into the individual. 



If the creative thought has been expressed by the forms of 



