Fig. 1. The lethal embryonic phenotype of clk-2(qm37) at 25°C. (A-D) Wild-type embryos; (E-I) qm37 mutant embryos. The very early embryonic development of the mutant (E,F) is indistinguishable from wild-type development (A,B); however, clk-2 embryos invariably arrest at different stages of embryogenesis and die subsequently with obvious morphological abnormalities (G-I), compared with the wild type (C,D).