定義： Living in the fluid medium (water or air) but unable to maintain their position or distribution independently of the movement of the water/air mass (adapted from Lincoln et al., 1998).
定義： An eye that consists of a cluster of three or four pit eyes that form a single structural unit but are separated from one another by pigment layers
定義： A compound eye with no separation between the crystalline-cone layer and the retinula, each rhabdom receiving light only from its own corneal lens.
