PLATE 81 



A 



B 



A. Tail of Col u mini guinea <!!). nest-mate of mutant -JO). age J9 days; shows normal 



whitish tail-hand in dark feathers. 



B. Tail of C. un'inco, mutant (20), age 7S days; shows a weakened whiti 



band, misplaced, in center of normal Hack-band. 



C. Tail of C. fjuinffi (10. sister to mutant), age 1 _'") 'lays. 



