Contents

04 May 1990
Vol 248, Issue 4955

About The Cover

Skeleton of a colony of the cheilostome bryozoan Steginoporella magnilabris. Features of individuals modules (zooids, each about 1 millimeter long) that are preservable in the fossil record are sufficient to discriminate between morphospecies that breed true and are genetically distinct. Thus paleontologists can study evolutionary patterns at the species level in this group. See page 579. [Scanning electron micrograph by Susann Braden, National Museum of Natural History SEM Lab, Smithsonian Institution]