COCOI HERON 93 
deal, but chiefly the Cocoi, and think there is some- 
thing to be said in support of Buffon’s opinion that 
they are wretched, indigent birds, condemned by 
the imperfection of their organs to a perpetual 
struggle with want and misery. In reality the organs, 
and the correlated instincts, are just as perfect as in 
any other creature, but the Heron is certainly more 
highly specialised and lives more in a groove than 
most species. Consequently when food fails him in 
the accustomed channels he suffers more than most 
other species. 
Much as the different species vary in size, from 
the Ardea cocoi to the diminutive Variegated Heron 
of Azara (Ardetta involucris), no bigger than a Snipe, 
there is yet much sameness in their conformation, 
language, flight, nesting and other habits. They 
possess a snake-like head and neck, and a sharp 
taper beak, with which they transfix their prey as 
with a dart—also the serrate claw, about which so 
much has been said, and which has been regarded as 
an instance of pure adaptation. 
A curious circumstance has come under my obser- 
vation regarding Herons. Birds in poor condition are 
very much infested with vermin; whether the ver- 
min are the cause or effect of the poor condition, I do 
not know; but such is the fact. Now in this region 
(the Argentine Republic) Herons are generally very 
poor, a good-conditioned bird being a very rare 
exception; a majority of individuals are much 
emaciated and infested with intestinal worms; yet I 
have never found a bird infested with lice, though the 
