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.