INTRODUCTION 5 



various diverging stocks have arisen, but only one stock 

 forms the channel through which organic evolution proceeds. 

 The diagram in figure 1 may serve to make the principle 

 more clear. The various hues both sohd and dotted rep- 

 resent new species that have arisen from the common 

 stock A. The dotted lines represent species that have 

 arisen but are off of the line of progressive evolution. These 

 forms may persist for longer or shorter periods and may give 

 rise to new and more complicated species, but they are not 

 in the direct line of evolution and therefore are not enduring. 

 The soHd hnes of the diagram represent the species which are 

 in the Une of progressive evolution. 



The question arises : why has organic evolution proceeded 

 along the lines that it, apparently, has chosen? The factors 

 involved in Natural Selection may account for the ultimate 

 destruction of the aberrant species and stocks, but is Natural 

 Selection sufficient to determine the course that organic 

 evolution has taken? Does Natural Selection supply an 

 element of progress, a something that has directed evolution 

 to a more and more complex end? This is a mooted point, 

 and it appears to me, as it has to many others, that Natural 

 Selection, by itself, is not sufficient to determine the direction 

 of organic evolution. If we accept Natural Selection as 

 the cardinal principle controlhng the direction of organic 

 evolution, then it is necessary to recognize a preordained 

 purposive factor in Natural Selection that carries us beyond 

 our powers of comprehension. Natural Selection can only 

 deal with that which has been formed; it has no creative 

 powers. Any directing influence that Natural Selection 

 may have in organic evolution, must, in the nature of the 

 process, be secondary to some other unknown factor. 



In attempting to determine the cardinal principle involved 

 in the origin of species, it appears reasonable to assume that a 

 number of factors combine to inaugurate those changes in 

 an organism that shall lead to the origin of new species. 



