OF THE TRAVANCORE HILLS. 369 
to the Central Himalayan race (and I suspect Mongolian birds 
from what Radde says are akin) with a greater tendency to 
deep rufous colouration and a more fully-feathered tarsus. 
From all I have seen of this sub-group of Buzzards, I am 
inclined to suspect that they are specifically of recent origin, and 
that the several species have not yet become fully differentiated. 
As a rule, it seems to me that when dealing with continental 
species (the conditions of insular life are different), it is only 
those that are past their prime, which we may expect to find 
clearly and sharply defined from their congeners, and without 
intermediate connecting links. While the group of species 
is young and still developing, the boundaries are still hazy 
and intermingled; it is only when decadence has commenced, 
and the interconnecting links have dropped out, that the several 
surviving species are found to be distinctly isolated. It seems 
to me probable that all those groups, in which the species are 
found, to grade imperceptibly into each other (a gradation, 
often, and, as I think, unphilosophically explained as cases of 
hybridism), are of comparatively recent origin, and that the 
more throughly isolated a set of species are the older they may 
primd facie be assumed to be. Of course, there are external cir- 
cumstances which will modify this general law as to the normal 
progress of species of life, but the law itself appears to me to be 
one of primary importance that has scarcely as yet attracted 
attention. 
To return to our Buzzards, and their supposed accidental 
melanoid varieties ; there is yet a fourth species to be noticed, 
and that is Archibuteo hemiptilopus, Blyth. 
Now it is very remarkable that this also has a black form, as 
dark as the darkest plumipes, or 5th stage feroa. 
I have very fully described one specimen of this species (a 
presumed female) (S. F. Vol. I, p. 315) whichis in the stage 
corresponding to my first stage of ferox. LIalso described 
(Joc. cit) from Mr. Hodgson’s drawing another specimen, a male, 
almost precisely in what I have called the 3rd stage ot ferow. 
Mr. Sharpe has figured and described (Cat. I. p. 199, Pl. VII. 
2) a specimen, supposed to be Hodgson’s type almost exactly 
in what I call the 4th or uniform brown stage, and I have now 
before me two others, one a female (presumably) in plumage 
intermediate between the 2nd and 3rd_ stages, and one a male 
(presumably) in the 5th or melanoid stage. Both these are 
from Thibet. 
The first measures :—Length, about 27; wing, 20; tail, 12; 
tarsus, 3°4 ; bill from gape, 2°0 ; mid toe and claw, 2°25 ; hind toe 
and claw, 1:9; bill, alonz culmen, from edge of cere to point, 1°3; 
hind toe claw along curve, 1:2; mid do. do. 0°75; inuer do. do. 1°1. 
