PREFACE 



TO THE GERMAN VERSION. 



Greater publicity* is herewith given to an Essay, 

 the contents of which will, I hope, prove interesting, not 

 only to the professed naturalist, but to all of the generally 

 well informed, who may be led to the consideration of 

 the Harmonies of development in Nature. On whose 

 account also I have endeavoured (with what success the 

 kind reader may determine) so to arrange the exposition, 

 that the least possible impediment should stand in the 

 way of any one desirous of becoming acquainted with the 

 mode of natural development in question. 



The special subject of this Essay is the fundamental 

 idea expressed by the words " Älternation of Genera- 

 tions^' or the remarkable, and till now inexplicable natural 

 phenomenon of an animal producing an offspring, which 

 at no time resembles its parent, but which, on the other 

 hand, itself brings forth a progeny, which returns in its 

 form and nature to the parent animal, so that the mater- 

 nal animal does not meet with its resemblance in its own 

 brood, but in its descendants of the second, third, or 

 fourth degree or generation ; and this always takes place 

 in the different animals which exhibit the phenomenon, 

 in a determinate generation, or with the intervention of a 

 determinate number of generations. This remarkable 



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* By the translation from Danish into German. 



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