1899] A ZOOLOGIST ON THE PRINCIPLES OF SCIENCE 429 



when ancestry is studied uncomplicated by nurture; that the 'mid- 

 parent ' is anything else than the actual parent ; that ' sports ' are 

 fundamentally different from the ordinary differences between in- 

 dividuals ; or that natural selection is restricted to the preservation of 

 sports" (p. 178). Galton's statistics are no evidence as to the effects 

 of inheritance, because inheritance is of many characters, not of one 

 only ; and in the statistics the effects of nurture are not sifted out. 



Lecture VIII. defends the pure natural selection theory of Darwin 

 against two criticisms. 



First, that, since natural selection "does not produce, but only 

 preserves the fitness which exists, it does not show why there should 

 be any fit to survive, but only why the unfit are exterminated." 

 Dr. Brooks says " the statement that selection could not act unless they 

 [the useful variations] existed is childish" (p. 184). Why? Because 

 " it is obvious." Very well ! then it is equally obvious that natural 

 selection does not " account for the whole history of " any character 

 Granting variations, natural selection is an adequate explanation of the 

 origin of species. But this is not the same as the evolution of our 

 present fauna and flora from a protoplasmic slime. Childish though 

 our curiosity may be, we cannot close our minds to the questions : 

 Why does living matter vary ? how is it that variations are inherited ? 

 is there a limit to variation other than that imposed by physical con- 

 ditions ? with many other questions that have nothing to do with the 

 operation of sorting into species, but which call for answer before we 

 can understand the mode of organic evolution. Because Darwin, as 

 Dr. Brooks justly urges (p. 187), wrote for a certain set of readers and 

 on a certain problem, this is no reason why we are never to proceed 

 beyond that problem. 



The second criticism is that many differences can have no selective 

 value in their incipient stages, whether of organic structure, as instanced 

 by Mivart, or of mental action, as instanced by Bomanes. This 

 objection can only be met by dealing with each instance in turn, and 

 showing that it has selective value. 



Lecture IX., " Natural Selection and the Antiquity of Life," 

 appeared in the Journal of Geology, and was dealt with in Natural 

 Science for October 1894. 



The remainder of the book considers the evidence for purpose in 

 nature, and first the argument from design as given by Paley. This is 

 stated in two forms. First (p. 258), "(1) Nothing accounts for watches 

 but mind. (2) Nothing accounts for living things unless it accounts 

 for watches. (3) Nothing but mind accounts for living things." This 

 is most obscure, and the phrase " accounts for " is ambiguous. If it 

 means " is the sole cause of," then the minor premise begs the question 

 or else is absurd. If we interpret (2) as, " The cause of living things 

 involves the cause of watches," which is true, then the only conclusion 

 is, " The cause of living things involves mind," even as it includes 



29 NAT. SC. VOL. XV. NO. 94. 



