w 



W 



Fig. 10. A, B, C, Sections through epidermis and cuticle, showing 

 three stages in growth of the imaginal disc (w) of a wing in the 

 caterpillar of a White Butterfly (Pieris). ep, epidermis; cu, 

 cuticle ; t, air-tube, whence branches pass into the developing 

 wing. In C, cu' represents the new cuticle forming beneath the 

 old one, and (p) the pouch within which the wing-disc (w) lies. 

 Highly magnified. After Gonin, Bull. Soc. Vaud. xxx. 



