Weismanris theory of Evolution (1891). 10 1 



organisms." Or again, — " The formation of new 

 species, which among the lower Protozoa could be 

 achieved without amphigony, could only be attained 

 by means of this process in the Metazoa and Meta- 

 phyta. It was only in this way that hereditary 

 individual differences could arise and persist V 



Now this doctrine is the most distinctive, as it is 

 the most original feature in Weismann's system of 

 theories. That it is of interest as an example of 

 boldly carrying the premises of a theory to their 

 logical termination, no one will deny. But as little 

 can it be denied that the very stringency of this logical 

 process brings the theory itself into collision with such 

 facts as those which have now been stated, and which, 

 as far as I can see, are destructive of the theory — or, 

 at any rate, of all that side of the theory which 

 depends on the doctrine of absolute stability. 



Take, for instance, the sequent doctrine that natural 

 selection is inoperative among the unicellular or- 

 ganisms. Here, indeed, we have another of those 

 doctrines which are so improbable on merely ante- 

 cedent grounds, that their presence might well be 

 deemed a source of irremediable weakness to the 

 whole theory of evolution of which they form integral, 

 or logically essential, parts. For seeing that the 

 rate of increase in most of the unicellular organisms 

 is quite as high as — and in most cases very much 

 higher than — the rate that obtains in any of 

 the multicellular, it becomes on merely antecedent 

 grounds incredible that the struggle for existence 

 should here not lead to any survival of the fittest. 

 When, for instance, we learn from Maupas that 



1 Essays, p. 296. 



