H. L. CARSON 37 



the functional gene pool from which recombinations are being 

 drawn. These combinations, encapsulated as individual organ- 

 isms, are confronted by natural selection at the local level. In a 

 broader sense, however, the gene pool includes all pools of the 

 species that are separated geographically and temporally from 

 one another. 



The pattern of sexual reproduction existing in a particular 

 local population constitutes its recombination system at that 

 point in time and space. This may be a relatively open or closed 

 system, depending on the chromosomal mechanisms and mating 

 system that prevail. Thus a species may have extensive genetic 

 recombinations available for selection in any one generation or 

 series of successive generations, or the potentiality for recombina- 

 tion may be partially closed or even locked up and unavailable. 

 These characteristics will be of very great importance in under- 

 standing ( 1 ) the past history of a species, ( 2 ) its present variabil- 

 ity, and (3) its potentiality for future evolutionary change. 



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Darlington, C. D. 1939. The Evolution of Genetic Systems. The Uni- 

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Dobzhansky, T. 1937. Genetics and the Origin of Species. Columbia 

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