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THE AMERICAN NATURALIST [VOL. XLH 



the leaf. The problem of localization of the new growth in such 

 cases is not discussed, nor have we, in fact, as yet any sufficient 

 clue to the matter. 



The growth of broken crystals in -saturated solutions is dwelt 

 on at some length. The remarkable similarity of this process to 

 regeneration in organisms is emphasized, more especially in the 

 light of the remarkable work of Lehman on fluid crystals. The 

 author apparently suspends judgment concerning the interpre- 

 tation of the resemblances of the two processes — whether we are 

 dealing with only an analogous process or whether the two phe- 

 nomena have fundamental properties in common. "Das Fur 

 und Wieder kann hier nicht erortert werden." 



Korschelt thinks that the loss of power to regenerate is a 

 general accompaniment of the degree of organization (Organi- 

 zationshohe), yet he points out that this is not universal, as 

 shown by the absence to regenerate in some forms and its pres- 

 ence in other closely related ones. In fact, the time-honored 

 statement of such a relation has very little weight in the face of 

 recent facts to the contrary. "When, for example, such a com- 

 plex organ as that of the eye of a salamander can regenerate 

 from a piece of the bulb, while the head of the planarian, Dendro- 

 coelum, fails to regenerate behind a certain level (where no 

 obvious change in ( )rgani/;it iunshohe is apparent) we may well 

 hesitate to lay any especial emphasis on such a generalization. 



The discussion of the phenomenon of regeneration as an 

 adaptation occupies only seven pages of the book. By adapta- 

 tion is meant in general not so much that the process is useful— a 

 fact too evident to dispute — but that in some way regeneration 

 has been acquired on account of its usefulness. Our author 

 would not, of course, adopt a teleologies! explanation, but as- 

 sumes instead the supposed alternative of the Darwinian ex- 

 planation of the origin of usefulness. Most students of the 

 subject have rejected this interpretation on what the reviewer 

 believes to be sufficient evidence. Korschelt 's somewhat cautious 

 attitude is summed up in the following statements. "Despite all 

 the difficulties that have been raised one can not escape the im- 

 pression that the power to regenerate and the liability to re- 

 generate stand in a causal relation to each other." "We find 

 that it is also the opinion of competent botanists that the inter- 

 pretation of regeneration as an adaptation is little to the point. 

 They agree with the zoologists mentioned above in this regard." 



