COCOI HERON 95 
Heron’s breast when it fishes in the dark, and which 
serves to attract the fish, or to render them visible 
to the bird. Naturalists have, I believe, dismissed 
the subject of this light as a mere fable without any 
foundation of fact; but real facts regarding habits 
of animals have not infrequently been so treated. 
Mr. Bartlett’s interesting observations on the Flam- 
ingoes in the Society’s Gardens show that the ancient 
story of the Pelican feeding its young on its own 
blood is perhaps only a slightly embellished account 
of a common habit of the Flamingo. 
I have not observed Herons fishing by night very 
closely, but there is one fact which inclines me to 
believe it probable that some species might possess 
the light-emitting power in question. I am convinced 
that the Ardea cocoi sees as well by day as other 
diurnal species; the streams on the level pampas 
are so muddy that a fish two inches below the sur- 
face is invisible to the human eye, yet in these thick 
waters the Herons fish by night and by day. If the 
eye is adapted to see well with the bright sun shining, 
how can it see at night and in such unfavourable 
circumstances without some such extraneous aid to 
vision as the attributed luminosity ¢ 
Herons of all birds have the slowest flight; but 
though incapable of progressing rapidly when flying 
horizontally, when pursued by a Hawk the Heron 
performs with marvellous ease and grace an aerial 
feat unequalled by any other bird, namely that of 
rising vertically to an amazing height in the air. 
The swift vertical flight with which the pursued 
