Slide showing diagram of 'Nucula nucelus'. Slide shows labelled diagram of 'Nucula Nucelus' with corresponding explanation. This is a type of mollusc. Title below image reads 'Fig. 548 - Nucula nucelus, the animal with the left mantle-lobe removed; a. ad. - anterior adductor; ar, anterior retractor; ft. foot; gl - gill; gon - gonad; l - levator; m. right lobe of mantle; mth. mouth; p. ad. posterior adductor; plp. palp; p.r. posterior retractor. (After Pelseneer)'. Late 19th - early 20th century