Columbia subject headings:
Echinodermata--Embryology.
Fertilization (Biology)
Meiosis.
Ovum.
Harvard subject headings:
Embryology--Echinodermata.
Fertilization (Biology)
Meiosis.
Ovum.
Princeton subject headings:
Embryology--Echinodermata.
Fertilization (Biology)
Meiosis.
Ovum.