THE RASORIAL FORM IN QUADRUPEDS. 259 
ox, the former were to have horns, and the latter a flow- 
ing tail, how closely would they resemble each other ! 
On such principles, that beautiful and astonishing va- 
riety, which constitutes one of the most remarkable 
features in the creation, would be destroyed; and if 
each type were to exhibit a// the properties or peculiar- 
ities theoretically belonging to it, we should have but 
five unvaried forms of living beings. This is the rock 
upon which many naturalists, who have not sufficiently 
reflected on the subject, are continually splitting. They 
argue after this fashion : — How can you maintain that a 
bat represents a mouse or a wading bird, when the first 
has wings, the second none, and the third has but two 
long legs ? or, how can you draw up a set of characters 
purporting to belong to the rasorial type, when many of 
the animals you bring forward in support of your 
theory, are actually without some of these characters ? 
Such reasoners appear to forget, that if a mouse had 
wings, it would be no longer a mouse — it would be a 
bat ; while the analogy of these quadrupeds to a wading 
bird, from being very remote, must not be made an im- 
mediate object of comparison, but must be traced through 
a number of intermediate analogical forms. 
(318.) The economy and instinctive dispositions of 
the rasorial type are stamped with many remarkable 
circumstances, deserving our deepest attention. So 
little, however, is known of such invertebrated animals 
as come under this denomination, that we must, in the 
following observations, be understood to speak more 
particularly of the rasorial types of quadrupeds and of 
birds ; thus selecting our illustrations from the most per- 
fectly organised, and the best known, of vertebrated 
animals. The economy of this type is in direct oppo- 
sition to that of the natatorial ; for it is strictly ter- 
restrial: we know not, in fact, a single instance where 
the individuals belonging to it frequent water or its 
vicinity. This propensity to live removed from that 
element does not, however, confine these animals to the 
bare ground ; for they either walk upon the surface with 
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