EEGENERATION 3 



one out of the other ; we can even penetrate down to the succession of 

 those delicate and marvellously complex processes which effect nuclear 

 and cell-division; but we are still far from being able to deduce, 

 except quite empirically, from the present state of a cell what the 

 succeeding one will be, that is, from being able to understand the 

 succession of events as a necessary nexus which could be predicted. 

 How a biophor comes to develop from itself the phenomena of life is 

 quite unknown to us ; we know neither the interaction of the ultimate 

 material particles nor the forces which bring it about; we cannot 

 tell what moves the hordes of different kinds of biophors to range 

 themselves together in a particular order, what molecular displace- 

 ments and variations arise from this, or what influence the external 

 world has, and so forth. We see only the visible outcome of an end- 

 less number of invisible movements — growth, division, multiplication, 

 reconstruction, and differentiation. 



As long as we are so far from an understanding of life no theory 

 of regeneration can be anything more than a ' portmanteau theory,' as 

 Delage once expressed himself in relation to the whole theory of 

 inheritance, a theory which is like a portmanteau in that one can 

 only take out of it what has previously been put in. If we wish to 

 explain the renewal of the aboral band of cilia in a Stentor, we first 

 pack our trunk, in this case the nucleus of the Infusorian, with the 

 determinants of the ciliated region, and then think of these as being 

 liberated by the stimulus of wounding, and being brought to and 

 arranged in the proper place by unknown forces to reconstruct the 

 ciliary region in some unknown way. No one could be more clearly 

 aware than I am that this is not an exhaustive causal explanation of 

 the process itself. Nevertheless, it is not quite without value, inas- 

 much as it allows us at least to bring the facts together in rational 

 order — in this case the dependence of the faculty of regeneration on 

 the presence of nuclear substance — under a formula which we can use 

 provisionally, that is, with which we can raise new questions. As 

 soon as we ascend higher in the series of organisms the theory gains 

 a greater value, for, while we leave altogether out of account any 

 answer to the ultimate question, and thus renounce for the present 

 the attempt to find out how the determinants set to work to call to 

 life the parts which they control, we are brought face to face with 

 other, in a sense, preliminary questions which we aoi solve, and the 

 solution of which seems to me at least not entirely without value. 



The first of these questions runs thus : Is the power of regenera- 

 tion a fundamental, primary character of every livhig being in the 

 sense that it is present everywhere in equal strength, independently 



B 2 



