"Cross-section of Arenicola. E., Epidermis; c.m., circular muscles; l.m., longitudinal muscles; b.c., body cavity; gl., gill; s., setae; n.p., nephridial pore; a.br., afferent branchial; e.br., efferent branchial; n., ventral nerve-cord, with blood vessels above; d.v., dorsal vessel; l.v., lateral vessel; s.i.v., sub-intestinal vessels; v.v., ventral vessel; g., gut." -Thomson, 1916

Arenicola

"Cross-section of Arenicola. E., Epidermis; c.m., circular muscles; l.m., longitudinal muscles; b.c.,…

"Cross-section through Ascaris. d.n., Dorsal nerve; n.c., non-contractile portion of muscle cells; c., cuticle; e., epidermis; l.l., lateral line; e.v., excretory vessel; m., contractile portion of muscle cells; v.n., ventral nerve; ov., ovary; ut., uterus; g., gut." -Thomson, 1916

Ascaris

"Cross-section through Ascaris. d.n., Dorsal nerve; n.c., non-contractile portion of muscle cells; c.,…

"Dissection of lob-worm from dorsal surface. m., Opening of retracted buccal cavity; i., gullet; gl., diverticula on first diaphragm; gl''., oesophageal glands; d., dorsal blood vessels; ef1., first efferent branchial; g., stomach intestine; n6., sixth nephridium; ef 13., thirteenth efferent branchial; af13., thirteenth afferent branchial; a., anus; af1., first afferent branchial; h., heart of left side." -Thomson, 1916

Lob Worm

"Dissection of lob-worm from dorsal surface. m., Opening of retracted buccal cavity; i., gullet; gl.,…