Evolution of Animal Life. 151 



The Lamarckian equation, on the other hand, might be 

 written ABHI=R. 



VI. The Failure of Darwixism. 



Now the Darwinian argument, as shown in equations 1, 

 2 and 3, is unquestionably sound. There is a competition 

 for life and there must be a survival of the fittest. It is 

 in equation 4, with the introduction of /, that the trouble 

 begins. For It belongs in this equation too, and R cannot 

 be had without A. It is therefore extremely doubtful 

 whether the theory provides for R. 



In other words, according to the Darwinian formida, 

 the results of natural selection are achieved ''in the long 

 run"; the amount of the variation selected by nature 

 through competition is, for any single generation, accord- 

 ing to this theory, extremely small ; and the analogy of arti- 

 ficial breeding Avhicli it invokes calls for the production first 

 of interfertile varieties, which shall harden in time into in- 

 tersterile species. But what is to prevent these varieties 

 from being swamped in the very first generation by cross- 

 breeding with the parent stem ? Again, if the struggle for 

 life results in the perpetuation of useful variations only, 

 why should not specific characters not belonging to this 

 class go on varying ? As a matter of fact, it is the ge- 

 neric rather than the specific peculiarities whicli are most 

 clearly advantageous. 



Mr. Darwin foresaw these difficulties, as what did not 

 that patient and candid investigator foresee ? They center 

 in the laws of heredity, variation and fertility or sterility, 

 all of which are as yet relatively unknown. In his acute 

 discussion of them, he followed still the analogy which had 

 led hi'm from the first, and assumed that the species created 

 by nature began with interfertile varieties. He argued in- 

 deed, in his " Origin of Species," that the intersterility of 

 species is not produced by natural selection, but is due to 

 unknown peculiarities of the reproductive system. 



VII. Darwinism as Perfected by Romanes. 



It was left for Dr. Romanes of London, to propound in 1886 

 what is, as Professor LeConte justly observes, i)erhai)S the 

 most important, if not the only important, addition which the 

 Darwinian theory has received, namely, the hypothesis that 

 natural selection operates upon those varieties only which 

 are not interfertile with other varieties ; in otlier words, that 

 such peculiarities of relative intersterility are the factors 



