Changes in the retina in different life stages of the eel. 2 μm thick plastic-embedded sections of eel retina from different life stages were stained with Richardson's Stain. It can be clearly seen that the thickness of the retina, and especially of the outer nuclear layer (rod cell nuclei), doubles between the glass and the silver stages of the life cycle. The size of the eye itself changes dramatically between the different stages, as indicated in the bottom panel, increasing ten-fold in diameter. Such changes must necessitate large scale remodelling of the retinal components. RPE, retinal pigment epithelium; ROS, rod outer segments; ONL, outer nuclear layer; INL, inner nuclear layer; OPL, outer plexiform layer; IPL, inner plexiform layer. Scale bar = 50 μm, all histology panels are to the same scale.