NOTICE BY TRANSLATOK. : 



The object of this little work, and the mode in which 

 the subject is treated, are so fully exhibited in the 

 Author's Preface, that it is scarcely necessary farther to 

 advert to them, excepting for the purpose of impressing 

 upon the reader, that he is not to expect in the account 

 here given of the phenomena intended to be comprised 

 under the term of ' Alternation of Generations,' or ' Alter- 

 nating Generations,' anything more than a mere outhne 

 of the subject ; nor is it proposed by the author to be 

 more than the rough sketch of a picture, to the filling up 

 of wliich naturalists may, perhaps, be the sooner incited 

 to direct their attention, by learning from the ingenious 

 speculations here set forth the probable existence of such 

 a mode of development in some form or other, in most, if 

 not all, of the lower classes of animals. ' Chamisso's Ob- 

 servations,' pubhshed so far back as 1819, on the apparent 

 alternations of generation in the Salpce, may perhaps be 

 considered as affording the earliest glimpse of the subject. 

 The subsequent observations of Sars on the development 

 of the MeduscB in 1828, and which were continued in 

 1835, 1837, and 1841, corroborated as they were in 

 great measure by those of Siebold in 1837 ; and the re- 

 searches of Loven in 1837, on the development of Cmri- 

 panularia, &c., considerably enlarged the nmnber of facts 

 relating to this mode of development. No one, however, 



