208 THE STORY OF THE BIRDS. 
also, have become flightless by the degeneration of 
the wings in size, but not in structure. 
The auks’ strongest tie is that to the gulls (21-19), 
already noted ; but véa the sea runners in the petrel 
forms a strain runs petrelward also (21-22). 
The petrels, like the penguins, are not closely con- 
nected, but tend to tie up slightly in many directions. 
A faint hint runs even to the plovers. In structure 
of head some petrel forms are like some pelican forms. 
They also, as noted, have an intimation of relation- 
ship to the heron forms, vea the albatross and flamin- 
go, as noted, but this is not to be stressed at all. 
We have now come to the heron forms by several 
different sources. Their kinship backward is evidently 
strongest toward the goose forms, and next, perhaps, 
toward the Pelican group. But downward to the 
birds of prey, va the secretary bird, is a strong tie 
—so much go that for years this last bird was thought 
to be a stork rather than a vulture. 
The Bird-of-Prey group, besides this last noted 
strain, is thought by some to be akin to the fowls 
(see arrow line) by the way of the carrion-eating vul- 
tures and the curassows. Some of the former have 
weak elevated rear toes like fowls, and some of the 
latter have hooked beaks with their nostrils opening 
through or at the edge of a skinny membrane at the 
base of the beak, like hawks, ete. A similarity of 
toe-tendon arrangement also exists between fowls and 
some birds of prey. 
The owls are placed with the birds of prey on ac- 
count of the structure of bill and claws, but their 
