Contents

30 April 2010
Vol 328, Issue 5978

About The Cover

Cover image expansion

COVER A late-stage Xenopus tropicalis (western clawed frog) tadpole, about 5 centimeters in length, with emerging hindlimbs. Through the skin of the head, the optic, trigeminal, and olfactory nerves, as well as the paired thymus and large blood vessels, are visible. A Report on page 633 describes the genome of this organism, which is an important model for vertebrate development. Photo: Siwei Zhang, Jingjing Li, Enrique Amaya