VI PREFACE. 



appropriation. Possibly, analogous enqui- 

 ries have long ago been instituted by those 

 more qualified for the task ; and, what has 

 appeared obscure in the nature of the ani- 

 mals now brought under consideration, may 

 already be elsewhere satisfactorily explain- 

 ed. 



The Figures, which will elucidate the 

 subject where verbal description fails, have 

 invariably been drawn from living PlanariaB 

 in motion, and generally after having fed, 

 as the most ample view of their organiza- 

 tion is then presented. Naturalists, who 

 take these animals indiscriminately from 

 their native abodes, may therefore find dis- 

 crepancies, resulting from a state of absti- 

 nence ; and variations still more conspicu- 

 ous may appear, from the unequal evolu- 

 tion of nascent parts. But experience will 

 speedily inculcate, where, after passing all 

 the successive stages, perfection at length 

 is gained. Nevertheless, the size is some- 

 what less than life, because Planariaa always 

 decline in a state of confinement. 



The name of any species distinctly re- 

 cognized is retained ; and if a new one is 

 bestowed on those where this is doubtful. 



