1915] Middle Membrane in Wings of Platyphylax 215 
BIBLIOGRAPHY. 
1. J. H. Comstock and J. G. Needham. The wings of insects. Amer. Natural. 
Vol. XXXII, 1899. 
2. J. Gonin. Recherches sur les métamorphoses de Lépidopteres. Bull. Soc. 
vaud. sc. nat. Vol. XXX, 1894. 
3. E. Kruger. Uber dir Entwicklung der Fligel der Insekten mit besonderer 
Bertcksichtigung der Deckflugel der Kafer. Inaug. Diss. Gottingen, 1898. 
4. W.S. Marshall. The development of the wings of a caddis-fly Platyphylax 
designatus. Zeit. wiss. Zool. Vol. CV, 1913. 
5. A. G. Mayer. The development of the wing scales and their pigment in 
butterflies and moths. Bull. Mus. Comp. Zool, Harvard, Vol. XXIX, 
1896. 
W. F. Mercer. The development of the wings in the Lepidoptera. Journ. 
N. Y. Entom. Soc. Vol. VIII, 1900. 
7. P. B. Powell. The development of the wings of certain beetles, and some 
studies of the origin of the wings of insects. Journ. N. Y. Entom. Soc. 
Vol. XII, 1904 and Vol. XIII, 1905. 
8. A. Rehberg. Ueber die Entwicklung des Insektenfligels. Jahresber. Gymnas. 
Marienwerder Programm, 1886. 
9. C. Schaffer. Beitrage zur Histologie der Insekten. Zool. Jahrb. Anat. 
Vol. III, 1889. 
10. C. Semper. Ueber die Bildung der Fligel, Schuppen und Haare bei den 
Lepidopteren. Zeit. wiss. Zool. Vol. VIII, 1897. 
il. G. W. Tannreuther. Origin and development of the wings of Coleoptera. 
Arch. Entwickmech. Vol. XXIX, 1910. 
12. W.L. Tower. The origin and development of the wings of Coleoptera. Zool. 
Jahrb. Anat. Vol. XVII, 1903. 
13. E. Verson. La Formanzione delle Ali nella larva del Bombyx mori. R. 
Stazione Bacol. Sperment. Padova, 1890. 
EXPLANATION OF PLATES XX-XXII. 
All figures drawn with a camera lucida. 
B. M., basement membrane. 
Cu., cuticula. 
Hyp., hypodermis. 
M. m., middle membrane. 
Per. cay., peripodial cavity. 
Per. mb., peripodial membrane. 
Pp. s., perpendicular strands. 
Tr., trichogens. 
Figures eight to seventeen inclusive have been drawn with the same magnifica- 
tion to allow an easy comparison of the relative thickness of the wing at these 
different stages of development. : 
PLATE XX. 
Fig. 1. Section through one of the two layers of hypodermis that form the internal 
wing rudiment. This figure shows the position of the crowded nuclei 
as more in the basal part of the layer. 875. 
Fig. 1A. Transverse section of the entire wing rudiment from which the pre- 
ceding figure was taken. X 105. 
Fig. 2. The middle part only of a section through an internal wing rudiment. 
The outer part of each layer of the hypodermis is not drawn. The two 
layers have nearly come together and only a slight open space can be 
seen between them. ‘The separation of the cells along their sides has 
started and a few of the narrow spaces between them can be seen. 
x 1100. 
