100 KINSHIP OF BIRDS, AS SHOWN BY EGGS. 
as we have seen, were doubtless much later than egg depo- 
sition, and it is hardly denied that these have done more to 
influence egg coloration than anything else. Now to-day it 
is known that few things are more variable than styles of 
modification. Climate and environment often entirely revo- 
lutionize building habits, not to notice the factor of variation 
here as elsewhere. Herein we face the full force of migra- 
tion on our subject, and halt in the presence of the fact that 
physiological trends and habits that affect the egg, both in 
time past and present, were set up in a far northern climate, 
in an environment now entirely changed and forever beyond 
our knowledge. The modern birds have come out of an un- 
known region, bringing with them their desire to get back— 
and their eggs marked to suit the foreign surroundings. We 
must feel that they have left behind many interesting phases 
of their original modification. The bird which in the arctics' 
long ago may have lined its nest with green moss or gray 
lichens may now floor it with flax in Dakota, or pad it with 
cotton in Texas ; and yet in either deposit a solid green or 
mottled grayish egg in keeping with the colors of “the old 
house at home.” So now unlimited tendencies to reversion 
may set back. 
With regard to modern reversions the occasional white egg 
now and then found, or entire white sets as noted among 
the Hawk-forms may be a kind of albinism or abnormal 
deficiency of color; but this is not always necessarily the 
case, 
It is-well known that a bloom or chalky deposit character- 
izes the eggs of many water birds—especially Grebes and 
Cormorants, some Grouse, and noticeably the Cuckoos, 
While it happens upon eggs of birds far apart it may in some 
measure indicate kinship. The Coccygomorphe or Cuckoos 
and Galline or Fowl groups are akin, according to Prof. 
Huxley. But the peculiarity is most striking in the Pelican- 
forms—whose affinities to other water birds are apparent 
only to the anatomist. But this roughness of the shell is 
