SYSTEM OF NATURE. 
121 
the aerial character, we should readily find expressions 
and apparent reasons for degrading the saltant; the Aptera 
would be insects deprived of their distinctive character— 
the power of flight, marsupials would be little better than 
reptiles, or birds without wings; mice might be called bats 
without wings, and lemurs only a degree above sloths. — 
This facility in assuming the superior importance of any 
given character, has led to very many tedious and unpro¬ 
fitable discussions. The respective claims to precedence 
of a bee and a mollusk have been sharply contested, and 
the complicated articulate structure and surpassing instinct 
of the former urged in its behalf. Instinct is not reason. 
Let instinct and the perfection of articulate structure be 
expressed by z y and let reason and the perfection of verte¬ 
brate structure be expressed by a: the bee will stand no 
chance of advancing even by a single letter nearer to man, 
while the cuttle-fish might reasonably claim an intermedi¬ 
ate place. This difficulty is but another proof of the error 
of laying down certain characters as of paramount impor¬ 
tance, and then making all others yield to them. 
The terrestrial radius ascends through the province Ver¬ 
mes or Annelida, the class Reptilia, the tribe Bruta, and 
probably the order or family of Megatheriidce, or fossil 
sloths ; and its companion radius, the ambulant, traverses 
the province Mollusca, the class Cataphracta, the tribe 
Belluae, and the order or family of Bradypidae, or recent 
sloths. In the first of these, the reptile character of crawl¬ 
ing or creeping on the ground is predominant throughout, 
but, like the aerial, it has four degrees or grades. The 
worms are without legs, and habitually reside in the earth; 
the snakes and lizards creep on the earth, the latter have 
legs, but so short in comparison to their body, and the 
