1917-18.] Germ-Band in the Egg of the Holly Tortrix Moth. 163 
From this stage the germ-rudiment rapidly assumes the form of the 
germ-band (figs. 9a, 96). The cells become still more columnar and 
closely apposed. The cephalic end becomes bi-lobed, forming the pro- 
cephalic lobes, and remains comparatively broad, while the body grows 
more slender. Meanwhile, down the whole length of the germ-band on 
its ventral (convex) surface a narrow median groove appears, by the 
sinking in and closing of which, and the multiplication of the cells at its 
base, the “ inner layer ” is formed (fig. 9c). Meantime, the “ segmentation ” 
(so-called) of the yolk is completed, and the yolk-balls tend to become 
somewhat polyhedral from mutual pressure (fig. 9a), while the entire 
vitellus continues to contract, assuming a rounded contour and always 
leaving empty a broad peripheral zone within the envelopes. 
Fig. 106 exhibits the embryo about fifty hours after oviposition. With 
the exception of the procephalic lobes, the embryo is fairly cylindrical in 
form, the ectoderm having curved round so as to embrace the inner layer, 
save on the dorsal side (fig. 10c). This is the stage strictly designated 
“the germ-band,” and in this stage E. noevana passes the winter, the 
inner layer, but not the ectoderm, having become completely segmented 
(%. ii). 
I wish to thank Dr Ashworth for his kindly supervision of my work, 
and the generous manner in which he has given me the benefit of his 
knowledge and experience throughout its prosecution. 
EXPLANATION OF FIGURES. 
All the figures, including those from the living egg, were drawn with the camera 
lucida. 
List of Reference Letters. 
A., amnion; C., chorion; F., female pronucleus; G.R., germ-rudiment; 
I.L., inner layer; M., male pronucleus; N., nucleus; P., periplasm; P.B., polar 
nuclei; P.L., procephalic lobes; R., Richtungsplasma ; S., serosa; V., vacuole; 
Y.G., ventral groove ; Y.M., vitelline membrane ; Y.P., vitellophags ; Y.S., vitellus; 
Y., yolk-body. 
Fig. 1. Sagittal section (not quite median) through an egg about an hour after 
oviposition (see p. 157). A single section contained everything shown in the figure^ 
with the exception of the second polar body, which occurred in the next section. 
x 150. 
Figs. 2 a and 26. Consecutive sagittal sections through the Richtungsplasma, 
about two hours and a half after oviposition (see p. 159). x 1000. 
