Fig. 3. Amphi-hairyA, Amphi-hairyB, Amphi-hairyC and D genes expression in amphioxus gastrulae by whole-mount in situ hybridisation. All embryos in dorsal views (A-C,E-G) have anterior towards the left. The lateral view (H) has anterior towards the left and dorsal upwards. In the transverse optical dissection (D), dorsal is upwards looking from a posterior position. The presumptive somitic bands are numbered and the arrows indicate expression domains in the neural plate (with the exception of D). (A) Amphi-hairyA expression within the anterior inner endodermal cell layer and the posterior neural plate. (B) Dorsal view of an Amphi-hairyB two- to three-stripe gastrula. (C) Dorsal view of an Amphi-hairyB three-stripe embryo. (D) Optical transverse dissection of the specimen in C showing the highest Amphi-hairyB expression levels at the edges of the neural plate (asterisks). The expression in the dorsolateral walls of the archenteron is shown by arrows. (E) Dorsal view of an Amphi-hairyB 4-stripe pattern embryo. (F) Dorsal view of a three-stripe pattern embryo stained for the Amphi-hairyC probe. (G) Dorsal view of a four-stripe embryo stained for the Amphi-hairyD labelled probe. (H) Lateral view of the gastrula in G showing the Amphi-hairyD gene expression as pre-somitic stripes.