Regeneration : Facts and Interpretations. 



By Professor August Weismann. 



My original intention in this essay 1 was simply to give an account of 

 some observations, recently published but probably not yet widely 

 known, which seemed to me to throw fresh light on the phenomena of 

 regeneration. It became necessary, however, to interweave with the 

 narrative some general remarks, in order to show on the one hand 

 how these and other additions to the data of our science harmonise with 

 the views I have previously developed, and on the other how these 

 views must be modified in order to bring them into accord with the 

 facts of the case, as we now know them. 



"We will first consider experiments made by Edmond Bordage, 2 

 Director of the Natural History Museum on the island of Keunion 

 (Bourbon), with regard to the regeneration of the beak in birds. 

 These deserve general interest, since they show that what has hitherto 

 been regarded as a rare exception is really the rule, and since thus 

 one argument against the interpretation of regeneration as an adaptive 

 phenomenon falls to the ground. 



In supporting this interpretation of regeneration I have previously 3 

 expressed the opinion that the regenerative power of a part is to be 

 considered, not as a direct and necessary expression of the nature of 

 the organism, but rather as a capability which, though it may be absent, 

 is found wherever it is necessary in the interests of species-preserva- 

 tion. The capability of a part for regeneration seemed to me to 

 depend, ceteris paribus, on whether the part was frequently liable to be 

 lost in the ordinary course of life, and also on its relative biological 

 importance for the animal. The weak and almost rudimentary limbs 

 of Siren and Proteus, which swim in snake-like fashion, are not replaced 



1 Translation revised by Prof. W. N. Parker. 



2 Gvmipt. Rend. Soc. Biol. Paris, July 9, 1898. 



3 "Das Keimplasma, eine Theorie der Vererbung," Jena, 1892. (Englisb Ed., "The 

 Germ-Plasni, a Theory of Heredity," London, 1893.) The idea there elaborated had been 

 previously more or less distinctly suggested from various quarters. Thus even Reaumur 

 pointed out that the power of regeneration was especially characteristic of animals whose 

 brittle body was frequently liable to ri.sk of breakage, and also of those, like earthworms, 

 which are liable to be partially devoured by others ("Mem. pour servir a 1'hist. insectes," 

 Paris, 1738). In modern times, Lessona and Darwin have developed the same idea. 



21 NAT. SC. VOL. XIV. NO. 86. 305 



