Fig. 3. The posterior limit of pharyngeal expression of AmphiPax1/9 (A-F), AmphiPitx (GO) and AmphiNotch (P-U) is shifted anteriorly by RA (C,D,J-L,R,S) and posteriorly by BMS009 (E,F,M O,T,U) compared to expression in control animals treated with DMSO (A,B, G-I,P,Q). Anterior to left. Arrowheads indicate the posterior limit of endodermal expression. Double arrowheads in I,K,L,O point to Hatschek's anterior left diverticulum, the precursor of Hatschek's pit, which is the amphioxus homolog of the vertebrate adenohypophysis. Scale bars=50 µm. Mid-neurula (18 hours)=A,C,E. Late neurula (20 hours)=G,J,M,P,R,T. Early larva (30 hours)= B,D,F,H,K,N,Q,S,U. Mid-larva (48 hours)=I,L,O.