No. 627] 



ADAPTATION 



345 



by which it comes to pass, we are wont to believe that the 

 reparative activities move directly toward the end which 

 we observe to be ultimately attained. Thus Driesch tells 

 us that 



we see with our own eyes that the organism can do more than simply 

 perpetuate variations which have occurred at random. 



Wliat we see with our own eyes, as I have already said, 

 is only a series of visible stages in the process of resti- 

 tution. We do not see the inmost morphogenetic proc- 

 esses, physical and chemical, by which this end is at- 

 tained. 



Perhaps it may seem that the foregoing explanation 

 merely resorts to the familiar expedient of throwing our 

 difficulties back into an invisible realm where they are 

 safely beyond the reach of scientific investigation. I 

 would say first of all that even this typo of explanation, 

 which at least speaks in the language of known facts, is 

 preferable to one which frankl>- aliandoiis scientific prin- 

 ciples altogether. And secondly, I would point out once 

 more the possibility that this hypothesis is one which 

 may in reality be put to experimental test. For any in- 

 dication of a profiting by ''experience," i. e., of a short- 

 ening of the time required to effect a given regulative 

 response, would harmonize well ^\■\\h the hypoihcsis that 

 the response was at first effected ihroimli T<'iitat i\f -icixs. 

 Indeed, such evidence, even now. is not wliolly laeking. 



It may be well to remind ourselves at this point that 

 the perfect regeneration of missing parts, or the com- 

 plete reconstruction of a mutilated embryo is after all an 

 exceptional phenomenon. Many animals almost entirely 

 lack the power of regeneration, while most injured eggs 

 either die or give rise to abnormal embryos. These facts 

 liarnioiiize best with the view that regenerative processes 



