264 THE INDUCTIONS OF BIOLOGY. 



twins. And here we seem forced to conclude, that the larger 

 functional variations produced by greater external changes, 

 are the initiators of those structural variations which, when 

 once commenced in a species, lead by their combinations and 

 antagonisms to multiform results. Whether they are or 

 are not the direct initiators, they must still be the indirect 

 initiators. 



88. That they are not in all cases, or even in most cases, 

 the direct initiators, is clear. Were they so, those unlike- 

 nesses which exist between plants that grow from seeds out 

 of the same seed-vessel, or between animals belonging to the 

 same litter, would be inexplicable. Here, all the antecedents, 

 structural and functional, appear to be alike for each of the 

 new organisms. Any deviations caused by structural con- 

 trasts or functional disturbances in the parents, must be 

 equally shared in by all simultaneously-produced offspring. 

 Hence, an explanation of the variations arising under such 

 conditions, has still to be sought. 



These are the variations termed " spontaneous." Not that 

 those who apply to them this word or some equivalent, mean 

 to imply that they are uncaused. Mr Darwin expressly 

 guards himself against such an interpretation. He says : 

 " I have hitherto sometimes spoken as if the variations so 

 common and multiform in organic beings under domestica- 

 tion, and in a lesser degree in those in a state of nature had 

 been due to chance. This, of course, is a wholly incorrect 

 expression, but it serves to acknowledge plainly our ignorance 

 of the cause of each particular variation." Not only, how- 

 ever, do I hold, in common with Mr Darwin, that there must 

 be some cause for these apparently-spontaneous variations ; 

 but it seems to me that a definite cause is assignable 1 . I 

 think it may be shown that unlikenesses must necessarily 

 arise between the new individuals simultaneously produced 

 by the same parents. Instead of the occurrence of such 



