62 THE METHOD OF DARWIN. 



exhaustiveness is his study of pigeons. 1 As 

 usual, he knew clearly what he was after, and 

 this gave him the power of selecting judiciously 

 the lines along which to make investigations 

 and of using to the best advantage the materials 

 he worked on. In his remarks on the search 

 for the cause of the modification of species, he 

 said, " Believing that it is always best to study 

 some special group, I have, after deliberation, 

 taken up domestic pigeons." With other ends 

 in view, pigeons might be studied in different 

 ways. But remembering his purpose, his work 

 on pigeons is a model of exhaustiveness as well 

 as of reasoning. He not only studied the vari- 

 ation of breeds, but sought its explanation by 

 a minute study of individual differences. He 

 considered the skeleton as well as the feathers, 

 and gathered facts and specimens from all over 

 the world. 



What is true of his study of pigeons is true 

 of his work on orchids. The adaptation of 

 flowers for cross-fertilization had interested him 

 for many years, and he had collected a large 

 mass of observations; but he was true to his 

 instinct : " It seemed to me a better plan to 

 work out one group of plants as carefully as I 



1 Variation of Animals and Plants under Domestication, 

 Chaps. V. and VI., pp. 137-235. 



