222
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Description. Body subspherical or slightly ovoid, 0-16 mm in greatest
transverse diameter, covered with uniformly distributed minute spines ;
anterior sucker 0.06 mm in diameter ; ventral sucker extremely small,
FIGS. 130-136. Larval gymnophallids. ( 1 30) Metacercaria (Gymnophallus) scrivenensis;
(131) M . (G.) maromae (redrawn after Lebour, 1911); (132) M . (G.) perZigena
surrounded by gelatinous wall (redrawn after T'alomhi, 1940) ; (133) (f. bursicola
metarerraria enveloped within thin grlatinous tunira (redrawn after Stunkard and
Uzniann, 1958) : (134) Metace?carm (Gym~rophaZZoitles) tokimsis (redrawn after
Fujita, 1925) ; (135) spororyst of Gercutia dichotomu enclosing developing rercariae ;
(136) fully developed fork-tailed C. dichotoma (redrawn after Lebour, 1911). CG,
Cephalic gland; E , eye-spot ; G P , genital pore ; 0, developing ovary ; T, developing
testis; V I T , developing vitelline gland ; V S , ventral sucker.