1903.] 



to the Theory of Evolu tion. 



305 



when gathered at least as far as the 12th or 13th whorl, and I doubt 

 whether even beyond this so late in the season, any further branching 

 would have taken place. A few branches were broken off, and these 

 were of course counted j there was no difficulty, however, in easily 

 ascertaining whether a branch had in any case been developed or not, 

 and the peculiarity of the 1st whorl was certainly not due to missing, 

 but to undeveloped branches. 



Table V gives the relation between branches to the whorl and 

 position for the whole of the 126 plants. In two columns to the right 

 are given the means and variabilities of the branches for each whorl. 



Now, whether we judge by mean or standard deviation, we see 

 a perfectly gradual change from whorl to whorl, which absolutely 

 precludes us from considering the number of branches to the whorl 

 as a pure homotypic character. We see a marked differentiation due 

 to position of the whorl on the plant ; the whorls are homologous but 

 not homotypic parts. 



Suppose, however, that we disregard our test for differentiation,* 

 and proceed to find a correlation table for the whole material as 

 homotypic. We have Table VI, for which I have to heartily thank 

 Dr. Alice Lee. 



The value found for the homotypic correlation from this table is 



p = -0-0064±0-0185, 



or, there is no sensible homotyposis at all. 



But we might have gone to the other extreme and taken only the 

 3rd, 4th, and 5th whorls, which have more nearly the same means and 

 standard deviations as homotypes. The result is Table VII, giving 



P = 0-7918±0-0129. 



It will be perfectly clear, therefore, as these two results ought to be 

 the same, if the whorls were true homotypes, that we may get any 

 result at all if we neglect differentiation.! The answer to this is that 

 no trained biometrician would call these whorls " undifferentiated 

 like organs " with the two right hand columns of Table V before him. 



* On the test for differentiation, see ' Biometrika,' vol. 1, p. 334. 

 f Bateson, ' Boy. Soc. Proc.,' vol. 69, p. 200. 

 VOL. LXXI. Z 



