ClipArt ETC
"Diagram of a gymnoblastic Hydroid. a., Stem; b., root; c., gut cavity; d., endoderm (dark); e., ectoderm; f., horny perisarc; g., hydra-like "person" (hydranth); g'., the same, contracted; h., hypostome bearing mouth; k., sac-like reproductive bud (sporosac); m., a modified hydranth (blastostyle) bearing sporosacs; l., medusoid "person." -Thomson, 1916

Hydroid

"Diagram of a gymnoblastic Hydroid. a., Stem; b., root; c., gut cavity; d., endoderm (dark); e., ectoderm;…