FIGURE 1.16. A CREEPING AMOEBA.

FIGURE 1.17. DIVISION OF AN AMOEBA.

FIGURE 1.18. OVUM OF A SPONGE.

FIGURE 1.19. BLOOD-CELLS, OR PHAGOCYTES.

FIGURE 1.20. SPERMIA OR SPERMATOZOA.

FIGURE 1.21. SPERMATOZOA OF VARIOUS ANIMALS.

FIGURE 1.22. A SINGLE HUMAN SPERMATOZOON.

FIGURE 1.23. FERTILISATION OF THE OVUM.

FIGURE 1.24. IMPREGNATED ECHINODERM OVUM.

FIGURE 1.25. IMPREGNATION OF THE STAR-FISH OVUM.

FIGURES 1.26 AND 1.27. IMPREGNATION OF SEA-URCHIN OVUM.

FIGURE 1.28. STEM-CELL OF A RABBIT.

FIGURE 1.29. GASTRULATION OF A CORAL.

FIGURE 1.30. GASTRULA OF A GASTRAEAD.

FIGURE 1.31. GASTRULA OF A WORM.