324 KELLOGG AND BELL 



bees (p. 214) and the occurrence of the curious malformations 

 of venation called by us " deformation" (p. 219) among drone 

 bees must be looked on as sports or truly discontinuous varia- 

 tions. The regular occurrence of a 4-segmented foot, per- 

 fectly complete, functional in those numerous specimens of 

 Blattidag (p. 296) in which natural regeneration has taken place, 

 may be looked on as an example of discontinuous variation. 

 Although no difference in tarsal segments less than that of one 

 is conceivable, it is quite conceivable that the foot with one 

 fewer than the normal number might be in such condition that 

 it would be obviously a 5-segmented foot with one segment 

 dropped out ; in other words that when compared with a normal 

 5-segmented foot it would appear to be a modification of such 

 a foot with some one segment and that readily determinable 



wanting. But that condition is not at all what appears after 

 the cockroach regenerates a foot. The new foot is only very 

 little, if any, shorter than the normal 5-segmented foot; one 

 cannot say that it is precisely this or that segment which is 

 lost. It is a new kind of foot, apparently just as capable, as 

 " fit," as useful as the 5-segmented kind. We have regularly 

 occurring, in these cases of regeneration, the development of a 

 wholly changed organ, similar as a whole to the old one, but 

 different from it in all its parts, this difference not being one 

 of incompleteness or serial addition or subtraction, but the 

 difference of newness. It is the regenerative mutation of an 

 organ ! * 



The Rigor of Natural Selection and Determinate Variation. 



The theory of determinate variation is based on the hypothe- 

 sis that fluctuating variations are not in all cases, nor necessarily 

 in any case, purely fortuitous and scattering but that because 

 of some intrinsic or extrinsic influence they tend to occur along 

 definite or determined lines. The need for the theory rests on 

 the claimed inadequacy of slight fortuitous variation in offer- 

 ing selection a sufficient " handle " for action. The greatest 

 logical difficulty with the theory is that none of the influences, 

 which are known or may be conceived of, is adequate to cause 

 such an effect as that of producing persistent determinate vari- 

 ations. In the case of any developing individual, determinate 



