[Figure 1A.] A sagittal section of an embryo of approximately the age of the one shown in figure 1. × 43.
[Figure 2.] A dorsal view of an embryo with five pairs of mesoblastic somites.
[Figure 2A.] A sagittal section of an embryo of the stage shown in figure 2. × 43.
[Figure 2B.] A transverse section through the headfold of an embryo of the stage shown in figure 2. × 43.
[Figure 3.] A dorsal view of an embryo with about fifteen pairs of somites. × 20.
[Figures 3A]-[3D]. A series of transverse sections through an embryo of the stage of the one shown in figure 3. × 43.
[Figure 4.] A surface view of an embryo with about twenty pairs of somites. × (about) 15.
[Figures 4A]-[4D]. A series of transverse sections through the anterior end of an embryo of the approximate age of the one shown in figure 4. × 20.
[Figures 4E] and [4F]. Two transverse sections through the thyroid gland of this stage; more highly magnified. × 102.
[Figures 4G]-[4M]. A series of transverse sections caudad to the preceding. Figure 4H, × 43; other figures, × 20.