FIGURE 1.32. GASTRULA OF AN ECHINODERM.

FIGURE 1.33. GASTRULA OF AN ARTHROPOD.

FIGURE 1.34. GASTRULA OF A MOLLUSC.

FIGURE 1.35. GASTRULA OF A VERTEBRATE.

FIGURE 1.36. GASTRULA OF A LOWER SPONGE.

FIGURE 1.37. CELLS FROM THE PRIMARY GERMINAL LAYERS.

FIGURE 1.38. GASTRULATION OF THE AMPHIOXUS.

FIGURE 1.39. GASTRULA OF THE AMPHIOXUS.

FIGURE 1.40. CLEAVAGE OF THE FROG'S OVUM.

FIGURES 1.41 TO 1.44. SECTIONS OF FERTILISED TOAD OVUM.

FIGURES 1.45 TO 1.48. GASTRULATION OF THE SALAMANDER.

FIGURE 1.49. SEGMENTATION OF THE LAMPREY.

FIGURE 1.50. GASTRULATION OF THE LAMPREY.

FIGURE 1.51. GASTRULATION OF CERATODUS.

FIGURE 1.52. OVUM OF A DEEP-SEA BONY FISH.