CHARACTERS OF THE RASORIAL FORM. 257 
creation. In no one instance do we find that suctorial 
types, like the natatorial, are fived, as are the Polypes 
and the barnacles, to one particular spot: free powers of 
locomotion, and these generally accompanied with great 
agility, are, consequently, among its chief characters. 
Nearly all the animals which, from imbibing their nour- 
ishment by sucking the juices of others, and whose struc- 
ture at the same time is very simple, are of this type: it 
might, from this fact, be termed parasitic, for it comprises 
almost every animal which usually bears that name. The 
intestinal worms, the common Cimewx, Pediculus,and Pu- 
lex, the gold wasps (Chrysis), the Acari, or harvest bugs, 
and the Cocci, or cochineal insects, are a few out of the 
multitude of examples which can be proved, by analysis, 
to be modifications of this primary type. Among qua- 
drupeds, this latter character is not strongly developed ; 
but every one knows the parasitic nature of the cuckow, 
and the cow-pen bunting of America (Molothrus pecoris 
Sw.); while the Gastrobranchus, among fishes, illustrates 
this peculiarity in the most striking manner. 
(317.) The nasoriat type, so termed in ornithology, 
is the third and last which enters into the aberrant cir- 
ele—which circle is always closed by the union of this 
type with the nararoriaL ; hence it follows, that both 
approximate in their general characters. First, as to 
the form and structure of rasorial types. They are, in 
general, remarkable for their size ; being inferior only to 
the natatorial. From these they are further to be dis- 
tinguished by the strength and perfection of their feet ; 
the toes of which, in vertebrated animals, are never 
united so as to be used for swimming. This perfection, 
however, is of a very peculiar kind ; since it is confined 
to the powers of walking on dry land, or of climbing 
among trees. These scansorial powers, in fact, although 
occasionally found in other types, are so very frequent 
and remarkable in this, that it may be considered one 
of the peculiarities of the rasorial structure. This is the 
type so remarkable for the greatest developement of 
tail; and of those appendages, for ornament or defence, 
S 
