THE PRIMITIVE ORIGIN OF THE WINGS 



139 



"As. however, the first wing-layers depend upon the wrinkling of the general 

 integument of the body through the increase in the upper layer, the further 

 growth of the wings depends in the later stages upon the wrinkling of the epi- 

 dermis of the wing-membrane even, which fact we also observe under the 

 microscope when the new wings drawn forth from the old covers appear at 



Fio. 153. Partial metamorphosis of Melanoplux femnr-rubrum, showing the five nymph 

 stages, and the gradual growth of the wings, which are first visible externally in 3, Bl>, 3c. Emerton 



