Pratt. — Imaginal discs. 
PLATE 2. 
Fig. 8. Cross-section of an embryo showing the origin of the mesoderm. 
X 130. 
Fig. 9. Sagittal section of an embryo showing the formation of the head- and 
tail-folds. X 100. 
Fig. 10. Sagittal section of an embryo showing formation of proctodeum. 
X 100. 
Fig. 11. Dorsal aspect of an embryo in which both proctodeum and stomodeum 
have been formed. X 100. 
Fig. 12. Semi-diagrammatic sagittal section of an embryo in which both proc¬ 
todeum and stomodeum have been formed. X 100. 
Fig. 13. Surface view, lateral aspect, of an embryo of the same stage as that 
of Fig. 12. X 100. 
Fig. 14. Cross-section through the stomodeum of an embryo of about the same 
age as that shown in Figs. 12 and 13. X 130. 
Fig. 15. Cross-section through the middle of the same embryo as the one shown 
in the preceding figure. X 130. 
Fig. 16. Cross-section through the proctodeum of the same embryo as that' 
shown in Fig. 14. X 130. 
Fig. 48. Cross-section of an old embryo, passing through the anus and showing 
the invaginations of the posterior genital discs. X 220. 
Fig. 49. Cross-section passing through the end-intestine and middle portion of 
the genital discs. From the same embryo. X 220. 
Fig. 50. Cross-section passing through the anterior genital discs of the same 
embryo. X 220. 
