CHAPTER V 



ATTEMPTS TO CLASSIFY AND MEASURE VARIATION: 



BIOMETRY 



The period from 1880 to 1900, following Darwin's death, was 

 marked by extreme speculation concerning evolution rather 

 than by inductive study of its phenomena. This speculative 

 tendency found its culmination in Weismann's brilliant es- 

 says, but his ideas, notwithstanding their brilliancy, failed to 

 win acceptance among such biologists as insisted on having a 

 substantial basis of well-ascertained facts on which to rest 

 their theories. Weismann's theories were accordingly dis- 

 tinctly on the wane when in 1900 they received support from 

 an unexpected source, the rediscovery of Mendel's law of 

 heredity, which now fully established seems to require for its 

 explanation some such system of determiners as Weismann 

 had hypothecated and located in the chromosomes. 



During this period of speculation about evolution, biolo- 

 gists had been looking in various directions for new tools 

 with which to attack the study of evolutionary problems. 

 The facts of development were more carefully studied and 

 accurately described than ever before, and more precise in- 

 formation was sought about the influence of environment 

 upon development and growth. Thus experimental embry- 

 ology and experimental morphology were born, to be followed 

 a little later by experimental breeding. Meantime, Bateson 

 was attempting to classify variations on morphological 

 grounds without reference to their causation, and Pearson 

 was seeking to measure variability so as to determine its 

 direction and rate of progress. 



Darwin had throughout nearly a lifetime collected all ob- 

 tainable facts about variation in animals and plants as a 

 basis for his generalizations concerning evolution and hered- 

 ity. Much of his data is contained in his work on the 



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