EXPLANATION OF PLATE V. 
Fic. 1—Enlarged dorsal view of prothoracic gland and _ its 
appendages in D. vinula: v, vestibule ; g s, glandular 
sac ; d, duct; #1, @, ¢, lateral tubes containing bunches 
of bristles ; 7 m!, retractor muscles of ¢!; rm, 1 m”, 
retractor muscles of #; p m v, protractor muscles of 
vestibule ; 7 m v, retractor muscles of vestibule ; 1 r mv, 
lateral retractor muscles of vestibule. 
kia, 2.—External view of aperture of gland, g a; and of lateral 
tubes, 7 ¢; v, vestibule pulled open. 
Fig. 3.—Bristles on low knob from within # or P. 
Fic. 4.—Dorsal view of glandular sac, g s, nat. size, showing pro- 
tractor muscles of vestibule, p mv; st, stigma; /}, 7, 
first and second pair of legs. 
Fic. 5.—Dorsal view of glandular sac in situ to show relations to 
nerve cord: g', gy’, first and second thoracic ganglia ; 
A, C, alimentary canal cut short and turned forward; s, 
silk glands. 
Fic. 6.—Transverse section of apex of ¢!, when retracted to show 
its bifid termination, 
Fic. 7.—Longitudinal section through duct, d, of gland; v, vesti- 
bule ; e c, external chitin; hk, hypodermis ; ¢ c, transi- 
tional cells ; » c, chitinous rods (rings) which keep duct 
open. 
Fic. 8.—Portion of duct under higher power: rc, as above; de, 
cells of duct: with rather enlarged nuclei and cell 
bodies. 
Fic. 9.—Glandular cells of sac: b m, sharply defined basement 
membrane ; ch, very thin chitinous lining covering free 
surface of cells. The large size and _ branching 
character of the nuclei are shown, and the vacuolated 
borders of the cells. 
