CHAP, xx SUMMARY AND CONCLUSIONS 297 



specimens of B may deal with the difficulty in several 

 distinct fashions. The swift B will run away from A 

 and make its escape. The cunning B will hide itself 

 from A and elude notice. The strong B will stand 

 up to A manfully, and, after a few struggles, will teach 

 A to seek his prey by preference among less warlike 

 creatures. There is no one means of survival in the 

 struggle ; there are several. At any time, for any 

 species, there are innumerable possible advantages. 

 Candidates for nature's examination can and do spe- 

 cialise. It seems therefore that fitnesses are pro- 

 duced, but fitnesses of manifold types. Progressive 

 improvement (given constancy of environment) every- 

 where results, but it results upon different lines, and 

 the clearest outcome of the process is the transition 

 from the monotony of a few types to an almost infi- 

 nite variety. Of course we must remember that 

 variation in other types constitutes a change in the 

 " environment " of any one type, whether the altered 

 neighbour was a former competitor, or a former ally, 

 or liable formerly to be preyed upon, or making prey 

 formerly of the type in question. It follows that a 

 constant environment, such as "progress" involves, 

 can only be affirmed in a relative and limited sense. 

 And therefore we must similarly qualify the con- 

 nected assertion of continuous organic advance and 

 improvement as the result of natural selection. 



A third difficulty strikes one in connection with 

 the lowest organisms. Certain shells or the human 

 physique have ceased progressing because they have 

 reached the allotted goal ; good, but why have the 

 lowest not moved up ? Experimental science refuses 

 to admit abiogenesis. Wherever life came from at 



