170 THE CONDOR | Vol. XXII 
many other species than currently recognized), parrots, Frogmouths, Potoos, — 
Leptosoma and lastly in the Wood Swallows among the passerines. The struct- — 
ure of the oil gland with its numerous coiled tubes secreting fluid into a com- _ 
mon chamber which in turn discharges the oil through one or many orifices 
Fig. 37. IMMATURE GREAT BLUE HERON OILING MANDI- 
BLES BY WORKING THEM IN POWDER DOWN PATCHES PRE- 
PARATORY TO PREENING CONTOUR FEATHERS. 
to the surface might suggest an origin through the amalgamation of a number 
of separate tubes opening separately. All this, however, is pure hypothesis 
that may be verified or overthrown by careful study of the embryology of 
these structures. ) 
Biological Survey, Washington, D. C., May 26, 1920. 
