262 THE GENESIS OF SPECIES. [Chap. 



the bow of a violin being drawn along their edges.^ The 

 results of these combined internal powers and external 

 inthiences might be represented under the synd)ol of 

 complex series of vibrations (analogous to those of suund 

 or light) forming a most complex harmony or a display of 

 most varied colours. In such a way the reparation of local 

 injuries might be symbolized as a tilling up and completion 

 of an interrupted rhythm. Thus also monstrous aberra- 

 tions from typical structure might correspond to a discord, 

 and sterility from crossing be compared with the darkness 

 resulting from the interference of waves of light. 



Such symbolism will harmonize with the peculiar repro- 

 duction, before mentioned, of heads in the body of certain 

 annelids, with the facts of serial homology, as well as 



^ In his recently published work on Man, ISh: Darwin has made some 

 very remarkable adniissions as to the existence of an internal force such as 

 is here contended for. Thus, in vol. ii. p. 388, speaking of certain modifi- 

 cations, he says : " In the greater numlier of cases we can only say that 

 the cause of each slight variation, and of each monstrosity, lies much more 

 in the nature and constitution of the organism than in the nature of tlu' 

 surrounding conditions." Again, sjieaking of the disappenra«ce of spots 

 and stripes in pigs, doer, and tapirs, he remarks : " "Whether this change 

 was ellected through sexual or natural selection, or was due to the direct 

 action of the conditions of life, or some other miJcnoum cause, it is impos- 

 sible to decide" {Op. cit. p. 305). In the first volume, p. 154, he says of 

 the exciting causes of modifications : " They relate much more closely to 

 the const itulion of the varying organisin than to the nature of the conditions 

 to which it has been subjected." He also speaks (p. 225) of "unknown 

 ditfercnces in the constitution" as the undoubted cause of certain degrees 

 of sterility. Finally, with regard to the transformation of specific clia- 

 racters we have the following noteworthy passage : " An unexplained 

 residuum of change, perhaps a large one, must be left to the assumed 

 uniform action of those unknown agencies, which occasionally induce 

 strongly-marked and abrupt deviations of structure in our domestic pro- 

 ductions."— ("Descent of Man," vol. i. p. 154.) In this ])a.ssage Mr. 

 Darwin seems to admit all that the author of this book need demand. 



