OFANIMALSANDPLANTS. 7 



sometimes provided with appendages for the very purpose of trans- 

 portation by the winds ; to say nothing of many other remarkable 

 distinctions that on careful examination become manifest. 



At one time, I thought of making the character of the embryo the 

 basis of arrangement in the present work; but in confining myself to 

 a record of facts personally observed, these led insensibly in a different 

 direction, and one more descriptive ; as contributions towards a men- 

 tally pictorial representation of the Earth's surface. 



Several classes of animals and plants seem to require each a sepa- 

 rate map to exhibit clearly their geographical distribution ; but the 

 accompanying four maps represent the principal variations, and may 

 serve to illustrate the whole subject. Regions are marked out only 

 where a centre of origin can be distinguished, and vary in relative 

 importance; some regions containing numerous centres of origin, in 

 other words, a multitude of peculiar species, each having its own geo- 

 graphical limits ; wdiereas, on a general map, a single boundary line 

 must be selected. 



An instance of this inequality occurs in the map of Fluviatile 

 animals ; Madeira being colored as a separate region, although con- 

 taining, as far as known, an Ancyliis only, an exceedingly diminutive 

 species of fresh-water shell, that seems peculiar. It is here neces- 

 sary to distinguish Madeira from islands that do not possess fresh- 

 water animals. 



