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07 December 1984
Vol 226, Issue 4679

About The Cover

A molecular marker of mesenchyme cell differentiation in the sea urchin embryo: in situ hybridization with a gastrula embryo section of a cloned single-stranded RNA probe specific for the CyIIa cytoskeletal actin gene. Transcripts from this gene are indicated by the light autoradiographic grains seen only in the secondary mesenchyme cells. See page 1153. [R. Angerer and E. H. Davidson, California Institute of Technology, Pasadena 91125; photo by K. Cox]