THE UNKNOWN FACTORS OF EVOLUTION. 8 1 



vail are attributable largely to the unnatural divorce of the 

 different branches of biology, to our extreme modern special- 

 ization, to our lack of eclecticism in biology. We begin to 

 grasp the magnitude of the problem only when side by side 

 with field and laboratory data are placed paleontological data, 

 as well as anthropological, including the unique facts of human 

 variation and the laws of human inheritance. For in modern 

 embryology certainly the most brilliant discovery is that the 

 physical basis of all inheritance is the same — and growing out 

 of this is the high probability that the laws of heredity are 

 the same in the whole organic world, with no barriers between 

 protozoa and metazoa, or between animals and plants. Both 

 Weismann and Spencer show themselves blind to this nexus 

 of fundamental uniformity when they draw certain lines of 

 division in inheritance where none exist in the visible heredi- 

 tary mechanism of chromatin and archoplasm. With these 

 discoveries in mind does not Weismann appear as much afield 

 when he maintains that the inheritance of acquired characters 

 is a declining principle in the ascent of life, as Spencer when 

 he maintains that it is a rising principle in the ascent of life ? 

 The first step then towards progress is the straightforward 

 confession of the limits of our knowledge and of our present 

 failure to base either Lamarckism or Neo-Darwinism as uni- 

 versal principles upon induction. The second is the recog- 

 nition that all our thinking still centers around the five working 

 hypotheses which have thus far been proposed ; namely, those 

 of Buffon, Lamarck, St. Hilaire, Darwin, and Nageli. Modern 

 criticism has highly differentiated, but not essentially altered 

 these hypothetical factors since they were originally conceived. 

 Darwin's 'survival of the fittest' we may alone regard as 

 absolutely demonstrated as a real factor, without committing 

 ourselves as to the 'origin of fitness.' The third step is to 

 recognize that there may be an unknown factor or factors which 

 will cause quite as great surprise as Darwin's. The feeUng 

 that there is such first came to the writer in 1890 in consider- 

 ing the want of an explanation for the definite and apparently 

 purposeful character of certain variations.^ Since then a simi- 



1 op. cit., 1891. 



