"Antambulacral surface of Asterias rubens. a, madreporite; a', the same magnified; b, anus." —…
"Asterias rubens. Digestive system. an, anus; card. st, cardiac division of the stomach; int. caec,…
"Apical disc of sea-urchin. In the centre is the periproct bearing the anus; around it are five genital…