Identification of novel notochord genes in Oikopleura. (A-AG) Microphotographs of Oikopleura dioica embryos hybridized in situ with antisense probes against the genes indicated at the bottom right of each row. The developmental stages tested are indicated in the column headings. Embryos are oriented with their anterior ends to the left and their dorsal sides up. Red arrowheads highlight notochord staining. The inset in (L) shows stained muscle cells.