LEE BARKER WALTON 85 



III. 



The application of statistical methods to problems of 

 biology has provided and will continue to provide facts of 

 decided value obtainable in no other way. Nevertheless, 

 the use of data "en masse" uncoordinated with experi- 

 mental methods can not solve the riddle of existence so 

 easily as some, at an earlier period at least, would have had 

 us believe. There are, however, investigations which 

 seem fundamental to the problem under discussion and 

 which may well be approached from the statistical side. 

 These relate to the influence of certain factors composing 

 the environment as well as to the part played by asexual 

 and sexual reproduction, corresponding in reality to close 

 and cross breeding, upon variability and size in organisms. 



Some studies undertaken in 1900 in connection with 

 the influence of food supply on variability^ based upon 

 the comparison of groups of Chrysanthemum leucanthe- 

 mum L., the common white daisy, as well as Perca flav- 

 escens Mitch., the yellow perch, indicated that the dif- 

 ference in variability as evinced by the coefficient of 

 variation for a group with a maximum food supply as 

 compared with a group having a minimum food supply, 

 was extremely small and well within the limits allowed by 

 the probable error. From this the inference was that ex- 

 ternal stimuli played an extremely unimportant part 

 under normal conditions as a cause producing variability 

 in general. 



Attempts were subsequently made to obtain data bear- 

 ing on the results of close breeding and cross breeding 

 which differ merely in degree from parthenogenesis and 

 amphimixis. The question is an important one, for if 

 cross breeding is only valuable in sorting out and combin- 

 ing existing characters, it not only obscures the facts, a 

 knowledge of which is necessary before progress can be 

 made in building up new characters, but results in no 

 actual advancement in cumulative evolution. Here the 

 material for study consisted of scalariform or cross-bred 

 and lateral or close-bred (parthenogenetic) zygospores — 



^Science, p. 728, 1907. 



