Fig. 6. Graphs showing the mean and standard error of the number of serotonergic cells in the animal plate of treated embryos. (A) Controls and treatments that block or enhance vegetal signaling. (B) Treatments that enhance the specification of ciliary band or aboral ectoderm. (C) Treatments that enhance the specification of oral ectoderm (D) Treatments of embryos in which vegetal signaling is blocked to eliminate endogenous specification of ectoderm. The control bars in A-C are the same data. Stars indicate treatments that produce changes that are significantly different from controls (P<0.01).