Expression of NvHbn. In situ hybridization using a 749 bp probe of hbn. The asterisks mark the blastopore or oral end. (a,b) Egg and early cleavage stages showing a lack of expression. (c) Blastula stage embryo showing expression everywhere except in the blastopore. (d) Mid gastrula showing lack of expression in the invaginating endoderm (en). (e,f) Lateral and oral views of a late gastrula, stage embryo. (g) Planula stage, showing strong expression around the future tentacles (arrow) and in the putative neurons (n) of the mid body. (h,i) Early polyp stage showing expression around the base of the tentacles (t). (j,k) Older polyp stages, where expression is confined to the base of the tentacles.