affinity of the keratin for the stain makes cells at 

 this stage of development appear nearly black 

 under low magnification. 



The cell shown in figure 341 is atypical in that 

 the keratin has flowed together into large, ir- 

 regular masses. The nucleus does not show and 

 the orange body with its blue nucleus is an ery- 

 throcyte on the surface of the cell. The general 

 appearance of the down-sheath cell is suggestive 



of a partially squashed cell but there is little 

 evidence beyond its atypical appearance to in- 

 dicate that this was the case. 



The barjjs and Ijarbules of the chick down are 

 lield by a thin layer of these epidermal cells 

 (fig. 343 A). Upon drying, the sheath breaks 

 readily, allowing these structures to spread and 

 assume the fluffy appearance characteristic of 

 down. 



180 



