Figure 2.

S. purpuratus developmental stages. (A) Pluteus stage, termination of embryogenesis (96 h; essentially the same as the 72-h stage at which the measurements of Fig. 3 were made). m, Mouth; s, stomach; sk, skeleton; cb, ciliated band; coelomic sacs (arrowhead). (Bar = 50 μm.) (B) Larva 3 weeks after feeding begins. (Bar = 250 μm.) (C) Close-up view of rudiment in a larvae at the same stage. r, Rudiment; v, vestibule; p, primary podia. (Bar = 100 μm.) (D) Newly emergent juvenile sea urchin. (Bar = 400 μm.)