194 APPENDIX II — INTENSIVE SEGREGATION. 



same time, or at a somewhat earlier time, what I call prepotential 

 segregation will divide the species into two groups that are prevented 

 for the most part from intergenerating ; and these separate groups, 

 gradually coming under the influence of different degrees, forms, and 

 combinations of the transforming principles, will in time become 

 strongly characterized species. It is not, however, necessary that all 

 or anv of these forms of transformation should cooperate with segre- 

 gation in order to produce a distinct species. The accumulated 

 effects of segregation, unaided by these principles producing intensi- 

 fication, would be sufficient to produce well-defined species; but it is 

 impossible that they should often remain unaided. 



7. Utilitarian and Non-Utilitarian Divergence. 



The principles of suetude and selection, though they are directly 

 related to the development of utilitarian characters, may produce in 

 the useful innate characters of isolated sections of the same species 

 exposed to the same environment, divergence that is not necessary 

 or advantageous ; and the effects of the other six principles are often 

 not only wanting in but opposed to utility. Assimilational transfor- 

 mation includes redundance of growth, which is not always, as well 

 as economy of growth, which is always, utilitarian. Unbalanced 

 elimination, amalgamation, and fecundity may be advantageous, 

 useless, or disadvantageous. We have, therefore, in these six prin- 

 ciples of transformation, abundant cause for the introduction of 

 non-utilitarian characters; and, when accompanied by independent 

 generation, they must be the source of multitudes of non-utilitarian 

 divergences. In the earlier stages of divergent evolution the non- 

 utilitarian distinctions are more abundant; for in the later stages 

 multitudes of them are weeded out by economy of growth, as has been 

 clearly pointed out by Mr. Romanes ;* and still others through com- 

 ing under new conditions in the environment or through some new 

 habit of intelligence, become useful endowments, and are brought 

 under the preserving and accumulating influence of natural selection 

 or of suetude. It should, however, be noted that the development of 

 useful specific differences is as much due to independent generation 

 as is the development of useless specific differences. Diversity of 

 suetude or of selection does not produce divergent evolution unless it 

 cooperates with independent generation. 



* Physiological selection, Journ. Linn. Soc, Zool., vol. xix, p. 383 



