Biological Fact and Theory

I SHARE Prof. Johnstone's inability to solve either crossword puzzles or Mendelian results (NATURE, Feb. 26, p. 319). But I do not think this should encourage him to decry the carrying out of breeding experiments by men who can properly interpret them. It seems reasonable to regard Drosophila as the sum of a number of factors arranged in a certain way, just as a crystal of alum is an aggregate of molecules orientated in a definite pattern, of atoms specifically arranged to give molecules, and of electrons to give atoms.