Pratt. — Imaginal discs. 
PLATE 1. 
Pig. 1. Longitudinal section of a segmenting egg, in a plane nearly coinciding 
with the sagittal plane of the embryo. X 78. 
Similar section of a somewhat older segmenting egg. • X 78. 
A portion of the section shown in the preceding figure, seen under a 
higher magnification. X 760. 
Sagittal section of a segmenting egg in which all parts of the peripheral 
layer of protoplasm are occupied by nuclei. X 78. 
A portion of the preceding section seen under a higher magnification, 
many of the nuclei in process of division ; the peripheral layer of 
protoplasm with shallow grooves surrounding the nuclei. X 760. 
A portion of a section of a segmenting egg showing the deepening of 
the grooves in the peripheral layer of protoplasm to form the cells 
of the developing blastoderm. X 760. 
A portion of a section showing the completely formed blastoderm. 
X 875. 
Fig. 2. 
Eig. 3. 
Fig. 4 
Eig. 5 
Fig. 6 
Fig. 7. 
