EVOLUTION OP THE COLORS OP BIRDS. 129 



The following brief definitions will explain the above 

 terms: 



A. Environ AL Segregation — Isolation due to the 

 relations of organism to environment. 



(a) Industrial Segregation. "Activities by which 

 the organism protects itself against adverse influences 

 in the environment, or by which it finds and appro- 

 priates special resources in the environment." 



1. Sustentational. " Different methods of obtaining 

 sustentation by members of the same species." 



2. Defensive. "Different methods of protection 

 against adverse influences in the environment." 



3. Nidificational. Differences in nesting habits in 

 the same species. 



(b) Ghronal Segregation. "Segregation arising from 

 the relations in which the organism stands to times and 

 seasons." 



4. Cyclical Segregation. Among certain insects 

 "the life cycles of the different sections of the species 

 do not mature in the same years." 



5. Seasonal Segregation. Change in time of flower- 

 ing or breeding of a section of a species. 



(c) Spatial Segregation. Isolation in space. 

 Geographical. Physical or climatic barriers to free 



intercrossing. 



Local. Due to the wide distribution of species with 

 inadequate powers of locomotion or migration. 



Spatial segregation may also be subdivided in con- 

 formity with the causes producing it, thus: 



6. Migrational, "caused by powers of locomotion in 

 the organism." 



7. Transportational, "caused by activities in the en- 

 vironment that distribute the organism in different dis- 

 tricts." 



8. Geological, "caused by geological changes divid- 

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