[ 6 ] 



temporaries, and from the obfervations of my fucceffors in the plea- 

 fing employment of cultivating the fcience of Natural Hiftory; for 

 it mud be evident to fuch as have maturely confidered its particular 

 pans and divifions, that our fcience is ftill far removed from a ftate 

 of perfection. The difficulty of inveftigating permanently diftinc- 

 tive marks for difcriminating natural bodies from each other, muft 

 be evident to every inquirer into the fubject : One great caufe of this 

 difficulty arifes from the luxuriant variety which, as regulated or in- 

 duced by various circumftances, nature has employed in giving co- 

 lours to animals; thefe fufFer variations from the feparate or concur- 

 rent effe&s of many caufes ; fuch as, whether the animals happen 

 to be in a wild or domeftick ftate, or varied by the intermixture 

 of nearly allied kinds, producing what are called hybrid races, or al- 

 tered by the influence of different climates. At the fame time, it is 

 well known, in diftinguifhing the fpecies of many kinds of animals, 

 particularly Birds, that there are no other marks of difcrimination 

 to be found except what are derived from difference of colour; while 

 it unfortunately happens that the fame fpecies are apt to put on dif- 

 ferent appearances, and to be cloathed in different colours, at diffe- 

 rent times of the year; according as they are either wild or tame; 

 in various ftages of their life ; in the different fexes; as they happen 

 to feed on different foods ; owing to the particular climates which 

 they inhabit; and from various other circumftances. It is likewife 

 obvious that many animals and vegetables, efpecially of marine pro- 

 duction, have not hitherto been accurately obferved through all their 

 changes of age and fex ; or have only been defcribed or pictured 

 from dead fpecimens, either dried, or fluffed, or preferved in fpirits, 

 or faked, or diftorted and even maimed by various means, either ac- 

 cidental, or intentionally, for the purpofes of deceit; this laft is moft 

 evident in fhells, which are frequently rendered colourlefs, or are 

 otherwife altered from their natural appearance. 



While- 



