Proboscis Proboscis stalk Collar Gill pores Branchial region Midventral ridge Trunk Anus

E DCM DBV SH LM VCM CCd CC BT T.S. collar of Sac. kowalevskii E N LM MG CON PCBD HV T.S. proboscis of Sac. otagoensis

T.S. posthepatic intestine Bal. australiensis T.S. collar of Sac. mereschkowskii E CC DBV PSH PBV LM N BT DNC DBV CG I LML VBV VNC

T.S. genital wings of Ptych. bahammensis G LS DBV DNC GW E GP LML I VBV VNC ANR PH BD AC EGV PS K CT T.S. through proboscis stalk of Balanoglossus clavigerus DLV

Hemichordate enteropneust key: ANR, anterior nerve ring AC, anterior extensions of collar coeloms (contain longitudinal muscles) BD, buccal diverticulum BT, buccal tube CC, collar coelom CCd, collar cord CG, ciliated groove CON, connective tissue CT, chondroid tissue DBV, dorsal blood vessel DCM, dorsal collar mesentery DLV, dorsal longitudinal vessel DNC, dorsal nerve cord E, epidermis EGV, efferent glomerular blood vessels G, gonad GP, gonopore GW, genital wing HV, heart vesicle I, intestine K, keel LM, longitudinal muscles LML, longitudinal muscle layer LS, lateral septum MG, middorsal groove PBV, peribuccal blood vessels PC, proboscis coelom PH, perihaemal cavities (contain longitudinal muscles) N, nervous layer PS, proboscis skeleton PSH, proboscis skeleton horns SH, skeletal horns VBV, ventral blood vessel VCM, ventral collar mesentery VNC, ventral nerve cord