6. THE PHYLA PORTFERA, CNIDARIA AND PIAATYHELMINTHES
219
varying number of cercariae and considerable amount of granular
brown material. Cercaria (Fig. 125) 0.27-0.32 mm long x 0.14-0-16
mm wide, spindle-shaped, moderately active, covered with fine cuticular
spines ; anterior sucker 0.03-0.04 mm in diameter ; ventral sucker,
0.02-0.04 mm in diameter, in posterior half of body; prepharynx
absent ; pharynx 0.015 mm in diameter ; esophagus short, intestinal
caeca large, extending to level of anterior border of ventral sucker;
with a group of penetration glands closely packed on each side of
anterior sucker, opening by four ducts on each side at anterior margin
of sucker ; excretory vesicle Y-shaped, with large arms extending
anteriorly to level of pharynx, filled with dense excretory granules
each measuring 0.005 mm in diameter.
Life cycle. Cole (1938) has expressed the opinion that C. cambrensis
may be the cercaria of Metacercaria (Gymnophallus) margaritarum but
this remains to be proven.
10. Cercaria (Gymnophallus) fulbrighti Hutton, 1952. (Figs. 126-129)
(Superorder Anepitheliocystidia; order Strigeatoidea; suborder Azygiata;
Cercaria fulbrighti was described by Hutton (1952) from Cardium
edule collected a t Millbrook, Plymouth, England.
Description of stages in mollusc. Sporocyst (Fig. 126) somewhat
irregularly ovoid, 1.416 mm x 0.768-0-880 mm, capable of independent
movement by means of projecting parts of body wall ; definite snoutlike structure situated anteriorly ; with relatively few fully developed
cercariae in any one sporocyst, five being the maximum number
observed ; both daughter sporocysts and cercariae develop within
mother sporocyst ; in gonad, digestive gland, and upper part of foot of
Cardium edule. Fully developed cercaria tailless (Fig. l28), uniformly
covered with cuticular spines, body 0-258-0.408 mm (average 0.328 mm)
long x 0.152-0.196 mm (average 0-160 mm) wide; anterior sucker
0.068-0.082 mm (average 0.072 mm) wide ; ventral sucker, 0.0620.076 mm (average 0.070 mm) wide, in posterior half of body; prepharynx absent ; pharynx 0.020-0.024 mm (average 0.022 mm) wide ;
intestinal caeca bulbous, reaching beyond anterior level of ventral
sucker.; excretory vesicle Y-shaped with arms extending to midlength
of esophagus ; flame-cell pattern 2[(2 + 2) + (2 + 2)]. Young cercariae
within some sporocysts with forked tail (Figs. 127 and 129).
Life cycle. The complete life cycle of Cercaria fulbrighti is not known.
Hutton (1952) has pointed out that there is a “remarkable similarity
between this larva and the adult stage of G( ymnophallus) choledochus
superfamily Fellodistomatoidea; family Fellodistomatidae)
219
varying number of cercariae and considerable amount of granular
brown material. Cercaria (Fig. 125) 0.27-0.32 mm long x 0.14-0-16
mm wide, spindle-shaped, moderately active, covered with fine cuticular
spines ; anterior sucker 0.03-0.04 mm in diameter ; ventral sucker,
0.02-0.04 mm in diameter, in posterior half of body; prepharynx
absent ; pharynx 0.015 mm in diameter ; esophagus short, intestinal
caeca large, extending to level of anterior border of ventral sucker;
with a group of penetration glands closely packed on each side of
anterior sucker, opening by four ducts on each side at anterior margin
of sucker ; excretory vesicle Y-shaped, with large arms extending
anteriorly to level of pharynx, filled with dense excretory granules
each measuring 0.005 mm in diameter.
Life cycle. Cole (1938) has expressed the opinion that C. cambrensis
may be the cercaria of Metacercaria (Gymnophallus) margaritarum but
this remains to be proven.
10. Cercaria (Gymnophallus) fulbrighti Hutton, 1952. (Figs. 126-129)
(Superorder Anepitheliocystidia; order Strigeatoidea; suborder Azygiata;
Cercaria fulbrighti was described by Hutton (1952) from Cardium
edule collected a t Millbrook, Plymouth, England.
Description of stages in mollusc. Sporocyst (Fig. 126) somewhat
irregularly ovoid, 1.416 mm x 0.768-0-880 mm, capable of independent
movement by means of projecting parts of body wall ; definite snoutlike structure situated anteriorly ; with relatively few fully developed
cercariae in any one sporocyst, five being the maximum number
observed ; both daughter sporocysts and cercariae develop within
mother sporocyst ; in gonad, digestive gland, and upper part of foot of
Cardium edule. Fully developed cercaria tailless (Fig. l28), uniformly
covered with cuticular spines, body 0-258-0.408 mm (average 0.328 mm)
long x 0.152-0.196 mm (average 0-160 mm) wide; anterior sucker
0.068-0.082 mm (average 0.072 mm) wide ; ventral sucker, 0.0620.076 mm (average 0.070 mm) wide, in posterior half of body; prepharynx absent ; pharynx 0.020-0.024 mm (average 0.022 mm) wide ;
intestinal caeca bulbous, reaching beyond anterior level of ventral
sucker.; excretory vesicle Y-shaped with arms extending to midlength
of esophagus ; flame-cell pattern 2[(2 + 2) + (2 + 2)]. Young cercariae
within some sporocysts with forked tail (Figs. 127 and 129).
Life cycle. The complete life cycle of Cercaria fulbrighti is not known.
Hutton (1952) has pointed out that there is a “remarkable similarity
between this larva and the adult stage of G( ymnophallus) choledochus
superfamily Fellodistomatoidea; family Fellodistomatidae)