"Diagram illustrating gills or branchiae. b.c., cavity in which the body fluids circulate; br., branchial filaments which are merely much thinned out-pocketings of the body wall (w); ex, the external medium–water–in which the oxygen is dissolved." -Galloway, 1915

Gills or Branchiae

"Diagram illustrating gills or branchiae. b.c., cavity in which the body fluids circulate; br., branchial…