cox, DARWIN AND THE MUTATION THEORY 441 



This I understand to be, in effect, a protest against deducing proof of 

 separate creations from the imperfection of the geological record, coupled 

 with an admission that saltation or mutation does, at least occasionally, occur 

 among existing living forms. I trust you perceive the importance of the 

 concession that naiura non facit saltum is not strictly correct as applied to 

 the present inhabitants of the world. 



Having noticed Mr. Darwin's repeated use of the words per saltum, I 

 now wish to revert to his frequent use of the words monster and monstrosity 

 and to call your attention to the fact that they are not always employed 

 with exactly the same meanings. Sometimes by "montrosity" he evidently 

 intends to indicate a mere deformity, of the nature of an accidental injury, 

 or aborted or perverted development, but more generally he refers to a 

 deviation from type wide enough, or discontinuous enough, to exclude it 

 from the category of variations to which he supposed the operation of natural 

 selection must be confined. Among domesticated animals and plants, 

 however, the word "monster," as used by him, often meant no more than the 

 word "sport." In most cases when he used this term or one of its deriva- 

 tives he took care to explain that monstrosities could not be qualitatively 

 separated from other kinds of variations. Thus, in writing to R. Meldola, 

 in 1873, he says : 



"It is very difficult or impossible to define what is meant by a large variation. 

 Such graduate into monstrosities or generally injurious variations. I do not myself 

 believe that these are often or ever taken advantage of under nature." * 



In the "Origin of Species" he wrote: 



"At long intervals of time, out of millions of individuals reared in the same 

 country and fed on nearly the same food, deviations of structure so strongly pro- 

 nounced as to deserve to be called monstrosities arise; but monstrosities cannot be 

 separated by any distinct line from slighter variations." ^ 



He frequently repeats this last statement and it is quite clear that he intends 

 to convey the idea that all variations are merely quantitative, at any rate he 

 failed to adopt a nomenclature that would enable his readers to judge as to 

 the degrees of difference he meant to indicate by such adjectives as "insen- 

 sible," "minute," "slight," "large," "wide," "sudden," and " abrupt," 

 as applied to variations. I am convinced, however, that he recognized the 

 fact that there were two different kinds of variations, namely, first, what 

 he oftenest called "individual variations," by which he referred to the ordi- 

 nary differences between the single organisms of the same group, or what 



1 " More Letters," 1903, Vol. I, p. 350. 



2" Origin of Species," 6th ed., p. 6, also p. 33. See also "Animals and Plants Under 

 Domestication," 2d ed., Vol. I, pp. 312, 322. Also "More Letters," 1903, Vol. I, p. 318. 



