16 



CONTINUOUS, OR DISCONTINUOUS ? 



[iNTROD. 



thorn into perfection. Of the objections which have been brought 

 against the Theory of Natural Selection this is by far the most 

 serious. 



CThe same objection may be expressed in a form which is more 

 correct and comprehensive. We have seen that the differences 

 between Species on the whole are Specific, and are differences of 

 kind, forming a discontinuous Series, while the diversities of en- 

 vironment to which they are subject are on the whole differences 

 of degree, and form a continuous Series ; it is therefore hard to 

 see how the environmental differences can thus be in any sense 

 the directing cause of Specific differences, which by the Theory of 

 Natural Selection they should be."> This objection of course in- 

 cludes that of the utility of minimal Variations 



Now the strength of this objection lies wholly in the sup- 

 posed continuity of the process of Variation. We see all organ- 

 ized nature arranged in a discontinuous series of groups differing 

 from each other by differences which are Specific ; on the other 

 hand we see the divers environments to which these forms are 

 subject passing insensibly into each other. We must admit, then, 

 that if the steps by which the divers forms of life have varied 

 from each other have been insensible — if in fact the forms ever 

 made up a continuous series — these forms cannot have been 

 broken into a discontinuous series of groups by a continuous en- 

 vironment, whether acting directly as Lamarck would have, or 

 as selective agent as Darwin would have. This supposition has 

 been generally made and admitted, but in the absence of evidence 

 as to Variation it is nevertheless a gratuitous assumption, and 

 as a matter of fact when the evidence as to Variation is studied, 

 it will be found to be in great measure unfounded. 



In what follows so much will be said of discontinuity in Varia- 

 tion that it will not be amiss to speak of the reasons which have 

 led many to suppose that the continuity of Variation needs no 

 proof. Of these reasons there are especially two. First there 

 is in the minds of some persons an inherent conviction that all 

 natural processes are continuous. That many of them do not 

 appear so is admitted : it is admitted, for example, that among 

 chemical processes Discontinuity is the rule ; that changes in the 

 states of matter are commonly effected discontinuously, and the 

 like. Nevertheless it is believed that such outward and visible 

 Discontinuity is but a semblance or mask which conceals a real 

 process which is continuous and which by more searching may 

 be found. With this class of objections we are not perhaps con- 

 cerned, but they are felt by so many that their existence must not 

 be forgotten. \ Secondly, Variation has been supposed to be always 

 continuous and to proceed by minute steps because changes of 

 this kind are so common in Variatioi^ Hence it has been inferred 

 that the mode of Variation thus commonly observed is universal. 

 That this inference is a wrong one, the facts will shew. 



