Vol. xl.] 128 
many other species with equally different habits. Apart 
from weights and measurements, the eggs of corazx, corone, 
cormx, and frugilegus, I consider have no pronounced 
external characteristics by which they could be safely 
separated. In the drawer which I exhibit will be found 
ten distinct forms of corax eggs, which have in every case 
been almost exactly matched with those of corone, cornia, 
and frugilegus—so closely in some cases, except for their 
size, that they might well be the produce of the same 
bird. 
Two or more forms are sometimes found in the same 
clutch. The eggs of C. monedula are oologieally furthest 
removed from this group. There is, however, one clutch of 
corni« eggs exhibited to-night which is very closely allied to 
monedula eggs, and these have widely separated roundish 
spots, a characteristic of the latter, which also differs from 
the eggs of the other four members of the genus by having 
a much paler ground-colour. This may be accounted for 
by the fact that they are generally deposited in dark places, 
and in the process of evolution have lost much of their 
colour. There is a distinct tendency in the eggs of this 
species to become leucitic, z. e. bluish white ; this is well 
demonstrated in the series exhibited. It is very rarely 
found that monedula eggs resemble those of the other 
members of the genus, and typical eggs are easily distin- 
guishable. Cyanic eggs, 2. e. blue or bluish-green eggs 
almost without markings, occur in each species, but appear 
to be a rarity in those of frugilegus, and I have never seen 
eggs of this genus absolutely free from markings, though 
they may occasionally occur. 
Erythrism has, I believe, been known to occur among the 
eggs of nearly all, and among those of frugilegus exhibited 
there is one egg in a clutch of five which is pure white with 
minute markings of reddish brown, which rather points to 
erythrism being a transition-stage, though somewhat abrupt 
in this case. 
Special attention is called to the eggs of the Corvide 
by Lechner in “ The Eggs of Birds breeding in the 
