MEASUREMENT OF NATURAL SELECTION 537 



twenty-one cases to seven the asymmetry of matured fruits is less than 

 that of the ovaries which do not complete their development. Taken 

 as a whole, the differences show an unmistakable tendency to fall far 

 to the negative side of the bar. 



Xot merely the degree of radial asymmetry of the ovary, but the 

 number of its locules which have an odd number of ovules, seems to 

 be of consequence in determining whether an ovary shall complete its 

 development. Ovaries with even numbers — 6, 8, 10, 12 — of ovules in 

 their locules have a better chance of developing to maturity than do 

 those with one or more locules with an odd number. The question is 

 too involved for adequate discussion, and I will leave the subject with a 

 mere reference to Fig. 7 which shows that in the 1908 series the reduc- 

 tion in the percentage of " odd " locules is a very material one. 



Eliminated. Matured. 



Fig. 7. Percentage of " Odd " Locules in eliminated and matured Ovaries 



of Staphylea — 1908 collection. 



The work just outlined has been rather drastically criticized on the 

 ground that studies on the selective elimination of organs can never 

 have any bearing on the problem of evolution. I think there is room 

 for differences of opinion on this point, but at present the purely mor- 

 phogenetic and physiological sides of the problem are of paramount 

 interest; our knowledge of facts is too meager to justify speculations 

 on so complex a problem as that of the origin of species. 



IV. Concluding Eemarks 

 In the paragraphs which have preceded these I have tried to set 

 forth honestly the results which have been secured in attempts to as- 

 certain by direct quantitative methods the intensity of the selective 

 elimination which may occur in nature. 



J 



What is the general significance of these results? What claim 

 have they to the special attention of scientific men? 



First, let us premise that the measurement of natural selection is 

 not synonymous with such an expression as the demonstration of the 

 natural selection theory. Upon the application of biometric methods 

 many supposedly valid biological theories have shrunken to nothing; 



vol. lxxvui. — 38. 



