340 The Alligator and Its Allies 



8b and 8c. Two sagittal sections of an embryo of this stage. 

 X 43- 



FIGURES 8d-8j. A series of transverse sections of the embryo repre- 

 sented in Figures 8 and 80. X 43. 



ga-^m. A series of transverse sections of an embryo somewhat 

 more advanced in development than the one represented 

 in the last series. X 43. 



FIGURES 10 and ioa. Dorsal and ventral views respectively of an 

 embryo with eight pairs of mesoblastic somites. X 20. 

 (Drawn chiefly by transmitted light.) 



FIGURE n. Dorsal view of an embryo with fourteen pairs of meso- 

 blastic somites. The area pellucida and the developing 

 vascular area are shown, the latter having a mottled 

 appearance. The pushing of the head under the blasto- 

 derm is also shown. X 20. (Drawn chiefly by trans- 

 mitted light.) 



FIGURES lia-n&. A series of transverse sections of an embryo of this 

 stage. X 43- 



FIGURE 12. Dorsal view of an embryo with about seventeen pairs of 

 mesoblastic somites. Part of the area pellucida is 

 represented. (Both transmitted and reflected light 

 were used in making the drawing.) X 13. 



FIGURES I2a-i2g. A series of transverse sections of an embryo of this 

 stage. X 43. 



FIGURE 13. Surface view of an embryo with about twenty pairs of 

 mesoblastic somites. X (about) 15. (Drawn with both 

 reflected and transmitted light.) 



FIGURES I3<z-i3/. A series of transverse sections of an embryo slightly 

 more developed than the one shown in Figure 13. 



X20. 



FIGURE I3g. A sagittal section of an embryo of about the age of the 

 one represented in Figure 13. X 20. 



14. Head of an embryo with one pair of gill clefts; ventro- 



lateral view. X 13. 



15. Profile view of the head of an embryo with three pairs of 



gill clefts. X 13. 

 FIGURES 150-15^. A series of transverse sections of an embryo of 



about the age of the one represented in Figure 15. X 20. 

 FIGURE I5/. A horizontal section through the anterior region of an 



embryo of the age of that shown in Figure 15. X 20. 



16. Surface view in profile of an embryo with four pairs of gill 



clefts. X (about) 12. 



