- 1. Ova from Psammechinus (sea urchin). Unfertilized ova, fertilized ova, early cleavage stages Lieder_5012e
- 2. Sea urchin embryology (Psammechinus miliaris), unfertilized ova w.m. Lieder_Ec201d
- 3. Sea urchin embryology, fertilized ova w.m. Lieder_Ec202d