In situ hybridization showing the distribution of dazl (A-H) and shh (I-P) mRNA in surface fish (A-D, I-L) and cavefish (E-H, M-P) eggs and early cleavage stage embryos. Eggs and embryos are oriented with the animal pole at the top except for B, F, J, H in which the animal pole is facing the viewer. A, B, E, F, I, J, M, N: One cell stage. C, G, K, O: Two cell stage. D, H: Four cell stage. L-P: Eight cell stage. Arrows indicate vegetal cortical localization of dazl mRNA. Scale bar: 300 μm.