H. L. CARSON 27 



frequency to zygotic frequency, predicted by the Hardy-Wein- 

 berg law, may thus be directly observed. 



This model may be elaborated somewhat; for instance, one 

 may intuitively grasp some of the enormous statistical conse- 

 quences of Mendelian heredity in sexual reproduction by drawing 

 zygotes from two or more fishbowls simultaneously. One may 

 attempt to diagram by this method the long-range effects of 

 selection on certain zygotic types. The elimination of a deleterious 

 gene, for instance, may be observed by extending selection over 

 a number of generations. In short, it is possible through such a 

 model to gain a crude measure of realization of how evolutionary 

 changes in gene frequency can occur through the media of mu- 

 tation, recombination and differential reproduction. 



Such models, however, have serious drawbacks. In many 

 ways, for instance, it is unsatisfactory to verbalize a mathemat- 

 ical concept like the above. The naturalist will also object to the 

 pictorial analogy, even for emphasis of a point of view, of the 

 species population to chips in a fishbowl. It is so crude as to make 

 it necessary to point out immediately the important ways in 

 which species populations do not behave like poker chips in a 

 fishbowl. The employment of the word "pool" in the expression 

 above, is nevertheless tremendously important to stress the 

 point that groups of individual organisms really possess a cor- 

 porate genotype, transcending that of the individuals. No other 

 word in common usage appears to come closer than "pool" in 

 expressing the nature of the phenomena involved. At this junc- 

 ture it seems unwise to invent a new one; rather it is better to 

 tell what a species pool is really like. 



The Local Population 



The term "gene pool" has also been used in a number of 

 senses. Thus, as is done very widely, one may refer to the total 

 gene resources, both past and present, of a species as its gene 

 pool. Whenever the term "gene flow" is employed, as is often 

 glibly done when neither actual genes nor actual flow are under 

 experimental observation, this broad view of the gene pool in 



