ClipArt ETC
"Diagrams to illustrate the development of one of the simpler types of sponge: I, the egg; 2, section of 16- to 32-celled stage; 3, section of later stage, a ciliated larva (blastula); 4, gastrula; 5, section through older larva which has become attached by the end containing the blastopore. New openings break through by the coalescence and perforation of the ectoderm and entoderm, and and a form results... a, archenteron; bl., blastopore; ec., ectoderm; en., entoderm; mes., mesenchyma; s, segmentation cavity." -Galloway, 1915

Simple Sponge Development

"Diagrams to illustrate the development of one of the simpler types of sponge: I, the egg; 2, section…