Fig. 1.

Results of genetic crosses: Cross (A; Cross #35 in Table 1) A homozygous white spined urchin crossed with a purple spined urchin produced all white spined F₁ offspring. In the F₂ generation, purple urchins returned in a 3:1 ratio. Cross (B; Cross #37 in Table 2) A homozygous white urchin crossed with a patterned green urchin produced all-white patterned offspring (similar in appearance to urchin a in F₂ generation). In the F₂ generation both patterned and nonpatterned white and colored offspring: (a) white, patterned; (b) white, nonpatterned; (c) purple-green, patterned; (d) purple-green, nonpatterned. Cross (C; Cross #15 in Table 3) Entirely purple cross produced purple F₁ and F₂ offspring. Cross (D; Cross #36 in Table 2) Purple urchin crossed with a patterned green urchin produce bicolored patterned F₁ offspring. In the F₂ generation both patterned and nonpatterned offspring: (a) purple, patterned; (b) purple-green, patterned; green, patterned (not seen); (c) purple, nonpatterned; (d) purple-green, nonpatterned.