18 



can be ascertained only by observation and comparison of facts, 

 the framing of hypotheses based upon those facts, and the 

 deductive test of the hypotheses. Thus by a selection of hypoth- 

 eses the fittest will survive. If Darwinism stands to-day seri- 

 ously discredited as a sufficient causo-mechanical explanation 

 of the fact of organic evolution, it is not on a priori grounds, 

 nor because it is, as supposed by some, atheistic or at variance 

 with the book of Genesis, but solely because, during the fifty 

 years of its rigorous testing by application to fact, it has been 

 found inadequate to explain all of the facts observed. 



Not the least value of Professor Kellogg's book is its candid 

 and, so far as space has permitted, adequate statement of both 

 sides of the question, and of the other theories now struggling 

 for recognition. Especially has the author rendered a service in 

 putting Plate's arguments against natural selection into a form 

 readily accessible to those who read German with difficulty, for 

 Plate's work constitutes one of the strongest assaults against the 

 Darwinian citadel. 



On page 234, when the author says, " If, in a species, a num- 

 ber of individuals show a certain congenital variation, this varia- 

 tion will probably be lost by cross-breeding with individuals not 

 having it, unless the individuals having it are in the majority or 

 unless they become in some way isolated from the others so that 

 they will breed among themselves," we are not sure from the 

 context whether he is stating his own belief or merely the argu- 

 ment of the isolationists. In any event, there seems to be here 

 a disregard of Mendelian light ; and a treatment of the bearing of 

 Mendelism on swamping by cross-breeding is not met with else- 

 where in the book. 



On page 330 the assertion, "Species-forming by sports and 

 discontinuous variations is obviously {sic) no theory to presume 

 to offer itself as a species-forming substitute for natural selec- 

 tion," seems strikingly intemperate in comparison with the treat- 

 ment of other theories in the book. Not " obviously," by any 

 means ; and least so to those who have taken the pains to check 

 up the results of field studies by experiments with pedigreed cul- 

 tures. On page 377 the mutation-theory of de Vries seems to 



