194 ON SYSTEMATIC ZOOLOGY. 
be paid to such matters; their advocates, very judi- 
ciously, do not insist on such considerations, nor do 
they attempt to point out in what way nature gradually 
passes from one group to another. That the reader, 
however, may be better able to judge for himself on the 
merits of a binary or dichotomous arrangement, we here 
present him with a table of the class of birds, as given 
by one who is, we believe, the only advocate of dicho- 
P] 3 
tomy * : — 
(Order I. Fisstrepes. Land Birds. Toes free, and formed for grasping 
or walking. 
(Tribe 1. Trrrestres. Tibial joint, feathered. 
(Sect. 1. AmpBuLarores. Three toes directed antially, and ‘fitted 
for walking or grasping. 
es LLINAD&. Bill arched from the 
I, Nostrils hid under an base; eggs numerous. 
arched covering, wing ¢ ‘OLUMBADX. Bill swollen at the 
i} 
| short. base, nearly straight, and sub- 
ulate towards the extremity. 
43 ( Accirirres. Bill and claws 
| strongly hooked, limbs strong, 
| | II. Nostrils exposed, or hid ae emarginate. Females 
H only by feathers. Passeres. Bill nearly straight 
at the gape, no cere. Males 
| largest. 
(Sect. 2. Scansores. Two toes directed antially, and fitted for 
climbing trees. 
| ee GRALLE. Waders, lower end of the tibial joint and tarsus 
nake 
LOrder II. Patmipepes. Water Birds. Toes wevbed to their extremity, 
and formed for swimming. 
(251.) The value of a theory can only be determined 
when we bring it into practice, and when, by following 
it down to its lowest details, we can judge how far it 
is agreeable with our ordinary conceptions of nature, 
and how far it answers the purposes of arrange- 
ment. With this view let us examine the foregoing 
table, which we must presume has been drawn up by 
one having “ distinct conceptions on positive and nega- 
tive characters ;” and let us do this, both with reference 
to its natural order, and to the help it gives for the de- 
termination of a species. We need not be long detained 
on the first, for it is difficult to name any two families 
of birds more unlike each other than the pigeons (Co- 
lumbade) and the eagles (Accipitres), which are here 
brought together. A greater violation of nature was 
* Dr. Fleming’s Philosophy cf Zoology and British Animals. 
