The effect of various steroid hormones on the in vivo induction of Xenopus ovulation. The left column represents the results of induction by hCG injection. Annotations underneath each column indicate substance and concentration for the induction of ovulation as following: Et0.01, ethanol 0.01%; DHP, 17,20β-DHP; P, progesterone; Tes, testosterone; And, androstenedion; E, 17β-estradiol. Each compound was added to 0.1 M NaCl at a final concentration of 1 μM except progesterone (additional high concentrations were examined at 10 μM; P10, 20 μM; P20, 40 μM; P40). After 24 to 30 hr incubation, the numbers of ovulated eggs were counted as described in the Materials and Methods. Each value represents the mean of data from more than three different females. The number of ovulated frogs per number treated is indicated over each column. Vertical lines indicate standard deviation.