Fig. 20. Through same region as fig. 19, shewing a groove (x) in the epiblast, probably artificially formed in the process of hardening.
Fig. 21. Through anterior part of tail region, shewing partial fusion of layers.
Fig. 22. Through posterior part of tail region, shewing more complete fusion of layers than fig. 21.
Figs. 23-25. Transverse sections of an embryo on the fifth day after impregnation.
Fig. 23. Through fore-brain and optic vesicles.
Fig. 24. Through hind-brain and auditory pits.
Fig. 25. Through anterior part of trunk.
Figs. 26-27. Transverse[TN 1] sections of the head of an embryo on the sixth day after impregnation.
Fig. 26. Through fore-brain and optic vesicles.
Fig. 27. Through hind-brain and auditory pits.