160 
TODUS, 
the pre-eminent type of the whole group, and 
which, although but a portion, retains, par excel- 
lence, the patronymic name. We have frequently 
called the attention of ornithologists to that peculiar 
property possessed by groups pre-eminently typical, — 
whether those groups be large or small, — of exhibit- 
ing a greater number of modifications, in the subor- 
dinate forms, than are to be found in the other 
divisions of their own circle. Lawrance, our emi- 
nent physiologist, long ago announced this fact in 
reference to the Caucasian race of Man, the most 
favoured and highly endowed of all that have ever 
lived. And it might be established beyond doubt, 
that this fact, first stated as an isolated and discon- 
nected remark, might be traced throughout the 
class of animals now before us ; sufficient, at least, 
to establish it as one of the laws of nature. There 
are more genera and sub-genera, — in other words, 
mere variations of form, — among the order Inses- 
sores, or perchers, than in all the other orders put 
together, and more in the genus Corvus, the type 
of all birds, than in any other yet ascertained. 
The sub-genus before us, like the groups just 
