CHAPTER IV. 
REPTILES DIVISIBLE INTO TWO CLASSES. 
Cuvier divided the reptiles into the true reptiles, 
“whose heart has two auricles,” — C. R. A. — and batra- 
chians, “ whose heart has but one auricle.”—C. R. A. This 
division appeared at the time unanswerable. All sub¬ 
sequent authors, whose works I have seen, adopt this 
dichotomous division. Mr. William S. MacLeay indeed 
proceeded a step further : anxious to make the Vertebrata 
subserve his general scheme of dividing all groups into 
five minor groups, he raised these divisions to the same 
rank as Mammalia, birds and fishes: this I always 
thought most unnatural. I compared genera of each 
class, — for instance, Salamandra and Gecko, — and they 
seemed almost identical; but still the similarity, perfect 
as it appeared, was far more than counterbalanced by the 
extraordinary discrepancy in the system of circulation. 
I recurred to the question again and again, and always 
with the same result: the double auricle and single auricle 
was a greater difference than I could reconcile. When 
Mr. Kirby’s c Bridgwater Treatise ’ made its appearance, 
I was smiling over that worthy gentleman’s quaint conceits 
and most marvellous hypotheses, and somewhat imperti- 
e 2 
