The Rhabdom of the Lobster Eye

Abstract

The spindle-shaped rhabdom of the lobster is a compact mass, 125µlong, by 25 µ by 25µ, at the widest point, composed of microvilli which extend from the 7 surrounding retinula cells. The characteristic feature is that the microvillar tubules are arranged in flat saddle-shaped plates, each about 2 µ. thick, which lie superimposed successively upon each other in a vertical stack along the optical axis, with the tubules of each plate at right angles to the tubules of the adjacent plates. The tubules are 60 to 100 mµ in diameter, and arise in groups of about 9 tubules from common stems where the edge of the plate meets the body of the retinula cell. The rhabdom appears to be partially separated from the cells by membranes and cisternae of the endoplasmic reticulum of the retinula cells. The commonest components of the retinula cells are rhabdomere vesicular spheroids, Golgi membranes, lysosomes, pigment granules, and endoplasmic reticulum. Thespheroids, Golgi membranes and lysosomes appear to be related. Large amorphous globules, which appear to be more abundant in darkadapted eyes, lie in rows in the axons of retinula cells and appear to be travelling along them.