The gametes show every gradation from complete similarity (isogamy) to a condition like that of Cutleria.
isogamy i·sog·a·my (ī-sŏg'ə-mē)
Conjugation between gametes of equal size and structure, or between individual cells alike in all respects.
A reproductive system characterized by the fusion of gametes (called isogametes) that are not distinguished in size or structure. Isogamy is found in some algae and other protist groups. Compare heterogamy.