Contents

03 April 1987
Vol 236, Issue 4797

About The Cover

Radial section through a compound eye of Drosophila illustrating its highly ordered and repetitive structure. Approximately 70 repeat units, or ommatidia, are shown. Each ommatidium contains eight photoreceptor neurons, seven of which are visible in any given plane of section. The determination of the various cell types during development depends on cellular interactions. See page 55. [Slide courtesy of Hermann Steller, Howard Hughes Medical Institute, Berkeley, CA 94720]