APLANOGAMOUS SEXUAL REPRODUCTION IN CARTERIA-EUGAMETOS (VOLVOCALES, CHLOROPHYTA)

Morphological details of sexual reproduction in Carteria eugametos (Vo lvocales, Chlorophyta) were studied under controlled laboratory condit ions. Protoplasts of the two pairing, flagellate cells were released f rom cell walls to become isogametes. Such gametes were nonmotile and s oon fused to form a completely immobile zygote. The zygote then secret ed a cell wall to enter the dormant period. After dark treatment, the zygote produced four, eight or 16 quadriflagellate germ cells, and a t ransparent vesicle enclosing all the germ cells was released from the zygote wall. This type of zygote germination and aplanogamy in C. euga metos is unique and may be related to its peculiar phylogenetic positi on within the Volvocales (Chlamydomonadales).