GB 
ap 
ab Ge 
Gp as 
Diagrams of transverse sections showing various mesenterial for- 
mulae. 4, supposed ancestor of Zoanthactiniaria ; B, Gonac- 
tinia; c,Haleampa; pb, form with graded cycles of mesen- 
teries but only six pairs perfect (e.g. Myonanthidae); §, an 
Edwardsia; -F, Parazoanthus; @G, Carlgrenia; 48, 
form with graded cycles of mesenteries, and sixteen pairs per- 
fect. Compare this with a further stage shown in Text-fig. 10. 
