Fig. 1. Samples and experimental setup. (A) Diagrammatic vertical section through a whole specimen of C. reniformis, showing location and orientation of choanosome (CHO) and ectosome (ECT) samples. ex, exopinacoderm; s, substrate. (B,C) Drawings of vertical sections through the ectosome and choanosome. ch, choanocyte chamber; ec, exhalant canal; ic, inhalant canal; m, collagenous mesohyl. (D) Drawing showing a sample attached to a glass coverslip (cs) with cyanoacrylate cement (cy). (E) Diagrammatic lateral view of experimental set-up in which the coverslip is held horizontally in a clamp (cl) and the deflection (d) of the sample under gravity is measured after a predetermined time period (45 s unless stated otherwise). [B and C are from Grassé (Grassé, 1973)].