DISCONTINUOUS VARIATION. 57 



mass of data concerning the repetition and division of 

 appendages in insects and Crustacea, colour markings 

 and colour variations in Lepidoptera, variations in the 

 number of legs of different species of Peripatus, the 

 occurrence of double monsters, and various other sub- 

 jects, but to these it is unnecessary to refer here. 

 Sufficient have been mentioned to indicate the general 

 nature and scope of the evidence, so that we are enabled 

 to enquire how far, if at all, it can warrant Bateson's 

 hypothesis as to the origin and production of discon- 

 tinuity in species. "We see that most of the evidence con- 

 cerns obvious abnormalities, generally in the direction 

 of increase in the number of parts, which have arisen 

 suddenly and apparently spontaneously. In practically 

 no case has any new structure arisen, but only a repe- 

 tition or misplacement of those already present, and so 

 it is difficult to understand how really new structures 

 and organs could have originated, even if it be admitted 

 that such abnormalities are of very frequent occur- 

 rence, and that they could succeed in permanently 

 establishing themselves. But first of all it is neces- 

 sary to point out that the large majority of these abnor- 

 malities are extraordinarily rare, occurring perhaps not 

 once in 100,000 or once in a million cases. What 

 chance have they, then, of establishing themselves on a 

 permanent footing? Bateson remarks, " An error more 

 far-reaching and mischievous is the doctrine that a new 

 variation must immediately be swamped," but he fails 

 to adduce one tittle of evidence to prove that it is an 

 error at all. This is simply because no such evidence 

 exists. It is true that some animals are prepotent over 

 others in procreating their characteristics, and their 



