120 
SYSTEM OF NATURE. 
its sides, and connecting the fore and hind legs, behind 
which it is also continued to the tail. When it is desirous 
of passing from tree to tree, it spreads its legs as widely as 
possible, and this skin is thus distended to the utmost; so 
that the animal is converted into a kind of parachute, sailing 
slowly downwards or with the wind, and protected from any 
risk of injury from falling by this admirable provision: the 
influence of the aerial ray is here exhibited in its fourth 
and last degree. It need scarcely be mentioned to the na¬ 
turalist, that a number of peculiarities in addition to wings 
are incident to the power of flying; of these increased re¬ 
spiration is one of great importance, and the absence or 
lightness of bones is perhaps scarcely inferior. 
We now come to a radius of a very different character : 
it is indissolubly linked with the aerial, yet scarcely in any 
degree partakes of its distinguishing attribute : its pro¬ 
posed name of saltant is not presumed to be perfect, or to 
express a character that is dominant throughout its course. 
The groups traversed by this radius are these: the province 
Aptera, the class Marsupialia, the tribe Glires, and the or¬ 
der or family Lemuridse : it need scarcely be added that 
these are twin groups to Pterota, Aves, Cheiroptera and 
Galeopithecidae, traversed by the aerial ray. 
If we abstract these pairs of groups from the general 
system, and suppose each pair to constitute a system of its 
own, we shall find considerable difficulty in deciding to 
which of each pair precedence or superiority is to be as¬ 
signed. Were we to insist on the superiority of the saltant 
radius, we should say that Galeopithecus is nothing more 
than an abnormal or flying lemur, that a bat is only a 
flying mouse, a bird only a flying marsupial, and a bee only 
a flying articulate : but were we to insist on the value of 
