172 APPENDIX I DIVERGENT EVOLUTION. 



supplemental to the laws of segregation already discussed, simply 

 reinforcing by artificial barriers the segregations that have their orig- 

 inal basis in nature. The chief forms to be enumerated are national, 

 linguistic, caste, penal, sanitary, and educational segregation.* 



CONCLUDING REMARKS. 



1. Impregnational Segregation a Cause of Divergence in both Us Earlier 

 and Later Stages. 



The negative forms of segregation would tend to produce extinc- 

 tion if they were not associated with the positive forms of segregation. 

 But in the case of organisms whose fertilizing elements are dis- 

 tributed by wind and water, the qualities that produce these nega- 

 tive forms of segregation are usually accompanied by those that 

 produce potential segregation, and potential segregation cooperating 

 with this free distribution results in positive segregation. But even 

 prepotential segregation, when produced by mutual incompatibility 

 between a few individuals and a numerous parent stock, depends for 

 its continuance and development on some degree of local, germinal, 

 or floral segregation, partially securing the intergeneration of the few 

 that are mutually compatible. On the one hand, impregnational 

 segregation depends on some degree of local, germinal, or floral segre- 

 gation which is a constant feature in most species ; and, on the other 

 hand, not only do these initial forms of positive segregation fail of 

 producing any permanent divergence till associated with impreg- 

 national segregation, but the more effective forms of positive segrega- 

 tion, such as industrial, chronal, fertilizational, sexual, and social 

 segregation, often depend on impregnational segregation, inasmuch 

 as the divergence of endowments which produces these depends on 

 impregnational segregation. Moreover, in all such cases, increasing 

 degrees of diversity in the forms of adaptation, and consequently of 

 diversity in the forms of natural selection, must also depend upon 

 these negative factors, which in their turn depend on the weak, initial 

 forms of positive segregation. 



Divergent evolution always depends on some degree of positive 

 segregation, but not always on negative segregation. Under positive 



* This completes the classification of the forms of isolation which are here pre- 

 sented as forms of demarcational segregation. It is probably correct to say that 

 with the exception of transportational and geological isolation, and perhaps some 

 cases of migrational isolation, all the forms of isolation so far discovered are, from 

 the first, more or less discriminative, and, therefore, segregative. Moreover, if 

 transportational or geological action plants an isolated colony of only a few indi- 

 viduals, the average type of the original stock is not fully represented in the colony 

 and, therefore, the effect is more or less segregative from the beginning. 



