Pratt. — Imaginal discs. 
i 
\ 
PLATE 6. 
Fig. 34. A slightly oblique sagittal section of an embryo in which the involu¬ 
tion of the head is completed. X 200. 
Fig. 35. Parasagittal section intermediate in position between those of Figs. 
33 and 34 and from the same embryo as those figures. X 200. 
Figs. 36-39. Cross-sections of the forward end of an embryo of about the same 
age as that shown in the preceding figures. The region of the embryo 
from which each of the sections is taken is indicated in Fig. 34 by 
the number of the figure representing the section. X 200. 
