Scanning electron microscopy of a harvestman, Homolophus biceps. that lacked both eyes and ocular tubercle revealed no indication of external damage or healing. Internally, light microscope sections showed no evidence of eyes. The brain had no or very degenerate optic nerve masses. The ventral nerve cord was also reduced. Of the three possible causative mechanisms i.e., physical damage, genetic change and biochemical disruption, the last is the most plausible.