1036 THE THEORY OF TRANSFORMATIONS [ch. 



several and constituent parts — head, body and tail, or this fin 

 and that fin — represent so many independent variants, then our 

 coordinate system will at once become too complex to be intelligible ; 

 we shall be making not one comparison but several separate com- 

 parisons, and our general method will be found inapplicable. Now 

 precisely this independent variability of parts and organs — here, 

 there, and everywhere within the organism — would appear to be 

 implicit in our ordinary accepted notions regarding variation; and, 

 unless I am greatly mistaken, it is precisely on such a conception of 

 the easy, frequent, and normally independent variability of parts that 

 our conception of the process of natural selection is fundamentally 

 based. For the morphologist, when comparing one organism with 

 another, describes the differences between them point by point, and 

 "character" by "character*." If he is from time to time con- 

 strained to admit the existence of "correlation" between characters 

 (as a hundred years ago Cuvier first shewed the way), yet all the 

 while he recognises this fact of correlation somewhat vaguely, as 

 a phenomenon due to causes which, except in rare instances, he can 

 hardly hope to trace ; and he falls readily into the habit of thinking 

 and talking of evolution as though it had proceeded on the lines of 

 his own descriptions, point by point, and character by character f. 



With the "characters" of Mendelian genetics there is no fault 

 to be found; tall and short, rough and smooth, plain or coloured 

 are opposite tendencies or contrasting qualities, in plain logical 

 contradistinction. But when the morphologist compares one animal 

 with another, point by point or character by character, these are 

 too often the mere outcome of artificial dissection and analysis. 

 Rather is the living body one integral and indivisible whole, in 



* Cf. supra, p. 1020. 



t Cf. H. F. Osbom, On the origin of single characters, as observed in fossil 

 and living animals and plants, Amer. Nat. xlix, pp. 193-239, 1915 (and other 

 papers); ibid. p. 194, "Each individual is composed of a vast number of somewhat 

 similar new or old characters, each character has its independent and separate 

 history, each character is in a certain stage of evolution, each character is correlated 



with the other characters of the individual The real problem has always been 



that of the origin and development of characters. Since the Origin of Species 

 appeared, the terms variation and variability have always referred to single 

 characters; if a species is said to be variable, we mean that a considerable 

 number of the single characters or groups of characters of which it is composed are 

 variable," etc. 



