596 Wm. S. Marshall, 



Fig. HA. Transverse section of a wing rudiment from the other side of 

 the same segment as that of preceding figure. a—a represents that portion 

 which gives the outer circle in surface view. b—b and c—c show relative greater 

 distance dorsal than ventral. x280. 



Plate XXVIII. 



Fig. 12. Later stage in the invagination, just as the disk Starts to evaginate. 

 From a transverse section of a larva 14 mm long. Cuticular layer not drawn. x 600. 



Fig. 13. Later stage of evagination of the disk, from a transverse section 

 of a larva, length not knowTi. The newly secreted chitin is shown extending 

 from the outer surface of the disk, through the peripodial pore and on to the inner 

 surface of the cuticular layer. x 600. 



Fig. 13 J. The entire pocket, other side of same larva as preceding figure, 

 showing the relation of the wing rudiment to the other parts. x 140. 



Fig. 14. Surface view of a wing rudiment from a larva 15 mm in length. 

 xl40. 



Fig. 14^4. Two sections from same larva as preceding figure but from 

 the opposite side of the body. Dorsal is below. x 140. 



Fig. 15. Surface view of the mesothoracic {Mes.) and metathoracic {Met.) 

 wing rudiments drawn in their natural relative position to each other. x 60. 



Fig. 15^4. Section of metathoracic wing rudiment of preceding figure, 

 from other side of body. x 140. 



Fig. 16. Surface view of a metathoracic wing rudiment from a larva 18 mm 

 long. The marking and bending is so complicated that they have only in part 

 been drawn. x 60. 



Fig. 16^4. Section through the metathoracic wing rudiment, other side of 

 body, of preceding figure showing the entire pocket. The cells of the hypodermis 

 are drawn diagramatically to more easily distinguish this from the other parts 

 of the figure. x 60. 



Fig. 165. Hypodermal layer, including wing rudiment, from the meso- 

 thorax of same larva. The cells are diagramatically drawn. This figure shows 

 the rudiment partially protruded from the peripodial cavity. x 60. 



Fig. 17. Surface view of the wing rudiments, now external. These are 

 drawn in their relative natural position to each other and represent the earliest 

 stage of external wing seen. x 40. 



Fig. 17^. Section of wing rudiment from one of those of preceding figure. 

 Cells drawn diagramatically. x 105. 



Fig. 18. Transverse section of entire pocket showing protruded wing and 

 its relation to the other parts. Slightly older than figure 17. x 90. 



Plate XXIX. 



Fig. 19. Section through part of a wing rudiment, a little older stage than 

 that represented in figure 17. The two layers of the hypodermal cells have 

 throughout part of the distance come together. A section of a wing vein is shown 

 cootaining a number of leucocytes, Leu. x600. 



Fig. 20. Surface view of two external wings in their relative position to 

 each other. x40. 



