Patterns of projection in the visual system of the fly. I. Retina-lamina projections

In each compound eye of the fly about 3200 ommatidia are arranged in a peculiarly distorted hexagonal array. Each ommatidium contains 7+1 rhabdomeres arranged in the asymmetrical pattern of the retinula. 7 fibers leaving each ommatidium are distributed onto 7 synaptic sites in the first optic ganglion (lamina ganglionaris), again arranged asymmetrically around the axis of the ommatidium. Taking into account the distortion of the macroscopical array and considering Kirschfeld‘s findings on the optical properties of the ommatidial lens, this complicated pattern of projection can be explained by the simple principle that all the fibers carrying information from the same point of the optical environment are united into one synaptic site of the lamina ganglionaris