Fig. 1. (A) Photograph of Tripedalia cystophora. There are four rhopalia located on the sides of the bell (arrow), which alternate with the four groups of tentacles at the corners. The lens eyes point inward, toward the center of the bell. Scale bar, 1 cm. (B) A photograph of a single rhopalium inside the rhopalial niche. Arrows indicate a pit eye and a slit eye. The slit and pit eyes are both identically matched on the other side of the rhopalium. (C) A photograph of an isolated rhopalium. Arrows indicate the upper and lower lens eyes. Scale bar, 200 µm.