PREFACE. 



prevails equally in the vegetable as in the animal 

 kingdom, and if rightly investigated would clear up 

 many of the difficulties attending the discrimination 

 of species, both in Zoology and Botany ; difficulties 

 which have arisen in consequence of many supposing 

 that certain organs are of equal importance in all 

 animals and plants, and that colour and habit are 

 always accidental. 



21, Lothian Street, 

 Edinburgh, February 28, 1838. 



