The exact neural projection of the visual fields upon the first and second ganglia of the insect eye

Abstract

In apposition eyes with fused rhabdomeres, six retinula cells of one ommatidium have short axons which terminate in a single cartridge. Each ommatidium corresponds to one lamina cartridge, the two ganglion cell axons of which, together with the long axons from that ommatidium and a fifth axon, proceed as a bundle through the lamina-medulla chiasma to form a cartridge of the medulla. The projection of the lamina cartridges upon those of the medulla forms a series exactly in order but reversed about the vertical plane. In the fly Calliphora, in which the optical axes of the rhabdomeres of a single ommatidium diverge, the existing description of the projection to the lamina is confirmed and extended to the medulla. As in fused rhabdomere eyes, the lamina cartridges project by bundles, each of which contains five axons, in an exact series but in reverse order, to the cartridges of the medulla.

Therefore in each type of eye there is an exact projection of the external environment upon the optic medulla.