Page:Proceedings of the Royal Society of London Vol 69.djvu/286

270 FIG. 2. Diagrammatic Longitudinal Frontal Section of a Larva about 18 days old.

ad., ce., st., stom., as before ; EcJi., invaginated ectoderm about to form the oral disc of the future Echinus ; hy., hydroccele ; l.a.c., left anterior coelom (ampulla of stone-canal) ; l.p.c., left posterior coelom ; m.v., madreporic vesicle (right hydro- ccele this is not in the plane of the figure) ; r.a.c., right anterior coelom ; r.p.c., right posterior coelom.

st.c.

FIG-. 3. Diagrammatic Transverse Section of a Larva about 18 days"old.

Names as before ; in addition, int., intestine; m.p., primary madreporic pore;

p.c., pore canal.