PRIMARY TYPES. 
typical characters of the Anniilosa is precisely that of 
the class of birds ; and both are distinguished, in their 
pre-eminently perfect examples, by having a body fur- 
nished with wings. A shellfish is the type of the 
Testacea, just as serpents are of the Reptilia ; and both 
these are without feet or fins, yet crawl upon their bellies. 
The Acrita and the Amphibia are the least organised of 
their own circles ; while the animals of the Radiata, 
like the fish, are pre-eminently aquatic. In this way 
has Nature represented the great divisions of the animal 
kingdom, in the class of Aves ; and has given us, under 
the form of a bird, another modification of that which 
we see in a butterfly. 
(7.) We have now sufficiently illustrated the station 
which the circle of birds occupies in the animal kingdom, 
and the analogies which belong to it as a class. Before, 
however, we proceed to explain the primary groups 
which compose this circle,let us advert to what has dready 
been said on the primary types of nature, and see how 
far they are exemplified, or how far they can lie traced 
in the objects before us. This investigation will be 
doubly instructive. It will tend to verify, in detail, those 
assertions which have been advanced in a general way ; 
it will also awaken the attention of the ornithologist to 
many peculiarities of structure and of habit ; and enable 
him, even in the investigation of species, to refer many 
shades of variation to one and the same cause, which 
would either pass unregarded, or be considered altogether 
anomalous. 
(8.) The primary types to which birds, no less than 
all other animals, as we conceive, may be referred, have 
been already expatiated upon.* But we are now to 
regard them only as they appear in one class ; and their 
definitions will consequently lose much of that vague- 
ness, and be stript of many of tliose exceptions, which 
It was impossible to avoid, when attempting to reconcile 
the innumerable variations they assumed in the different 
groups of the entire animal kingdom. The names by 
• Classification of Animals, p. 241. 
B 4 
