- 1. Chicken, 24 hour, t.s. with neural groove, notochord, germ layers Lieder_8201f
- 2. Frog, gastrula, sagittal l.s. shows germ layers, dorsal lip, yolk plug Lieder_8303f
- 3. Frog, early gastrula, sagittal l.s. shows formation of germ layers and dorsal lip Lieder_Em607f
- 4. Frog, later gastrula (yolk plug stage), sagittal l.s. with germ layers, yolk plug, blastocoel, Lieder_Em608f