408 MERISTIC VARIATION. [part i. 



touching the false attribution of the character of individuality to 

 members of Meristic Series. 



(8) Discontinuity in digital Variation. 



The evidence that the Meristic Variation of digits may be 

 discontinuous is often rather circumstantial than direct. If for 

 example in the case of the Horse any one chooses to suppose that 

 every polydactyle horse had in its pedigree an indefinitely long- 

 series of ancestors in which the size of the extra digit progressively 

 increased, it would not be easy to produce direct evidence that this 

 was not the fact. But as regards the human examples such evi- 

 dence is abundant, many of the most marked cases being the 

 offspring of normal parents and there can be no reasonable doubt 

 that the same would be found true of other animals. 



But it may fairly be replied that until it shall have been shewn 

 that formations like those described as variations may be estab- 

 lished in a natural race or species the contention that the Varia- 

 tion of digits may be discontinuous is so far weakened. To this I 

 would reply by referring to the case of Cistudo, Chalcides, and the 

 other similar examples ; for though in respect of these forms the 

 evidence is sadly imperfect yet it plainly indicates that very 

 distinct and palpable variation may be found between different 

 individuals. And since it is actually known that there may in 

 these points be considerable differences between the two sides of 

 the body it may safely be assumed that at least the same differ- 

 ences may occur between parent and offspring. 



We may therefore take it that there is in these cases some 

 Discontinuity of Variation, though until some one shall have 

 examined statistically such cases as that of the Box-turtles or of 

 the Kittiwakes, as to the magnitude of the Discontinuity it is not 

 possible to speak. If hereafter Discontinuity shall be shewn to 

 occur in many such cases it will be difficult to resist the sugges- 

 tion that similar numerical diversity elsewhere characterizing the 

 digital series of various forms may have come about by similarly 

 discontinuous Variation. 



(9) Relation of the facts of digital Variation to the problem of 



Species. 



This relation is both direct and indirect : direct, inasmuch as 

 some of the conditions seen to occur as variations are not far 

 removed from those known as normals in other forms ; and indi- 

 rect, since those strange and paradoxically regular dispositions of 

 digits which are found among the variations bear witness to the 

 influence of the principles of Symmetry, and prove that there are 

 modes in which Variation may be controlled and may produce a 

 result which has the quality of regularity and order of form 

 independently of the guidance of Natural Selection. 



