We could not ascertain whether infection occurs in the gonadal tissue or after the ova have been released into the
coelenteron. But, as the anemones were kept in artificial (and so zooxanthellafree) seawater in sterile flasks, and as spawning occurred in air, we can be certain that the zooxanthellae were of maternal origin, and that infection occurs prior to release into the surrounding seawater and hence prior to fertilization.