78 BREWSTER'S WARBLER. 



other is unknown, the experiments may be complicated and obscured through 

 the chances of impurity of the parent stock. The long twelve-month intervals 

 between successive generations, too, would place further obstacles in the path 

 of him who tried to solve this problem by breeding the birds in confinement . 



Mr. Brewster, arguing in 1881 in favor of the hybrid theory of H. leuco- 

 bronchialis, closed his brief with the following words: "The bars are down; 

 the gate stands open; 'he who runs may read.'" Yes, the gate stands open, 

 but what I read is a sombre inscription over the portal: 



LASCIATE OGNI SPERANZA, VOI CH' ENTRATE ! 



