Pratt.—I maginal discs. 
PLATE 7. 
pigs. 40-44. Cross-sections of the forward end of the same embryo as that 
shown in the preceding four figures. The region of each section is 
indicated in Eig. 34, PI. 7, by the number of the figure which repre¬ 
sents the section. X 200. 
Fig. 45. Frontal section passing through an invaginating thoracic disc. X 340. 
Eig. 46. Similar section of a completed thoracic disc. X 340. 
[There is no Figure 47. Figures 48-50 are on Plate 2.] 
I 
