Fig. 2. A dorsal view of an embryo with five pairs of mesoblastic somites.

Fig. 2a. A sagittal section of an embryo of the stage shown in figure 2. × 43.

Fig. 2b. A transverse section through the headfold of an embryo
of the stage shown in figure 2. × 43.

Fig. 3. A dorsal view of an embryo with about fifteen pairs of somites. × 20.