CHAPTER 1 

 INTRODUCTION TO THE METHOD 



A scientific historian writing at some future time about the growth of biology in the 

 nineteenth, twentieth and perhaps twenty-first centuries might be expected to begin his 

 account somewhat as follows : 



'The nineteenth century was a period of great intellectual activity in biology, 

 carried on it is true by a limited number of people but containing among them some 

 of the most powerful minds of the age. The perfecting of the compound microscope 

 was the most significant technical development, by means of which, for the first time, 

 animal histology and plant anatomy, together with the descriptive facts of life history 

 of the principal organisms of both kingdoms, could be adequately explored. On the 

 theoretical level the theory of evolution, coming as it did concurrently with this, and 

 based as it was in the hands of Darwin on the accumulated content of several centuries 

 of morphological observation of living and extinct plants and animals, wound up as 

 it were thejDurely descriptive phase of these sciences and paved the way for the experi- 

 mental period which was to follow. 



'The effect of the theory of evolution on human thought as a whole was revolutionary 

 and in many ways catastrophic, but this aspect of the history of ideas need perhaps not 

 be discussed by the merely scientific historian. Within biology itself the effect, though 

 actually profound, was superficially less marked. The great achievements of the 

 pre-Darwinian period, namely, the establishment of workable principles of nomen- 

 clature, description and classification, together with the recognition of the nature of 

 fossils and of their use for the compilation of the geological time scale, remained almost 

 unaffected in their factual content although profoundly influenced by the new con- 

 ception of their purposej( The quest for phylogenetic significance became a conscious 

 aim to be pursued almost to the exclusion of all else towards the close of the century, and 

 under it the descriptive aspects of morphological biology expanded rapidly) with the 

 renewed vigour and interest which the change of aim awakened. The methods by 

 which this aim were pursued remained, however, substantially the same as those 

 available to Darwin himself until, with the twentieth century in sight, the change from 

 observation to experiment set in. 



'This change was closely associated with the gradual recognition, not by isolated 

 individual workers but by the scientific world as a whole, of the need for an objective 

 study of the facts of variation as the next step required by the Darwinian theory of 

 evolution. This need was first effectively voiced by Bateson in the celebrated intro- 

 duction to the Materials for the Study of Variation of 1894, and it led directly to the re- 

 discovery in 1900 of the work of Gregor Mendel. 



'The effect of Mendel's papers at this their second -appearance was at first to obscure 

 the connexion between evolution and the study of variation owing to the necessary 

 preoccupation of geneticists for the next few decades with establishing the rules of 



MFC T I 



