DISCONTINUOUS VARIATION. 53 



hitherto generally held, since Darwin first gave ex- 

 pression to it, is that almost all variations are very 

 slight, and form a continuous series. It is only by their 

 very slow accumulation, therefore, under the action of 

 Natural Selection and other agencies, that species as we 

 know them have been evolved. This view of Bateson's 

 is so striking and important that it behoves us to ex- 

 amine it at some little length. It will enable us to ob- 

 tain a clearer idea of Bateson's views if we indicate his 

 system of classification. Thus he points out that varia- 

 tions are divisible into two classes, substantive and 

 meristic. Substantive variations are variations occur- 

 ring in the actual constitution or substance of the parts 

 themselves. Meristic variations, on the other hand, are 

 those which relate to the number of parts in organisms. 

 For instance, the flower of the Narcissus is commonly 

 divided into six parts, but through meristic variation it 

 may be divided into seven parts, or only four. Never- 

 theless, there is in such a case no perceptible change in 

 the tissue or substance of which the parts are made up. 

 On the other hand many Narcissi, N. corbularia, for 

 example, are known in two colours, one a dark yel- 

 low, and the other a sulphur yellow, though the 

 number of parts and pattern of the flowers are identi- 

 cal. This is, therefore, an example of a substantive 

 variation. 



Bateson considers that there can be no doubt that 

 these two classes of variation are essentially distinct 

 from each other. It is obvious that all cases of meris- 

 tic variation are also cases of discontinuous variation, 

 whilst cases of substantive variation are much more fre- 

 quently continuous than discontinuous. It is to be noted 



