Smithsonian Report. 1936. — Pycraft 



PLATE 3 



Reciprocity in Development. 



The results of the persistent pressure of a graduall.v elonsatins windpipe against the anterior border of 

 the keel of the sternum. A, Bewick's swan; B, a crane, and the course of a still greater elongation where 

 little or no resistance is presented; E, Phonygama; F, spoonbill, G, Manucodia. 



