THE INCUBATION OF HENS' EGGS 



187 



cutting the meiahrancs within. Accoriiin<;- to Polilman' 

 "the acti\e liiuscuhir a<;i'nt in hreakin"- tht' slicll conies ahont 



Fig. \)2 



Appearance of a ehick ell"ll)i\'n aflrr sixly hoiir.s in an inr'ul)ator. 

 (CVnutesy ft" Kansas Am-icult ni al I^xjua inient Statirtn.) 



Fig. 93 



Appearance of a ehick enibryo after seventy-two hours in an incu))ator. 

 (Courtesy of Kansas Agricultural Experiment Station.) 



' Anatomical Record, vol. xvii, No. 2. 



