6. THE PHYLA PORIFERA, CNIDARIA AND PLATYHELMINTHES
253
anterior one-third of body; two testicular anlagen globular, one on
each side of pyriform structure (identity unknown) , behind ventral
sucker; duct leading from pyriform structure to cirrus situated immediately anterior to ventral sucker ; excretory vesicle Y-shaped with
arms extending to between caecal tips and ventral sucker, stem pearshaped.
Other information. Nothing else is known about C. tenuans. Although
Cole appeared to be convinced that this parasite caused the death of
Mytilus edulis, in my opinion this hypothesis should be accepted with
caution since he only found six out of 300-400 dead mussels to be
infected.
40. Unidentified ‘ I Sporocyst ” of Nicoll, 1906. (Fig. 167)
(Taxonomic position undetermined)
During an examination for parasites in Cardium edule from the
vicinity of St. Andrews, Scotland, Nicoll(1906b) reported the occurrence
of a most unusual “ sporocyst ” in the hepatopancreas and on the
adjacent intestine. From his description, which is summarized below,
it would appear that he had found miracidia in the process of metamorphosing into rediae rather than sporocysts since it contains a
pharynx ; however, the fact that the “ daughter sporocysts ” (rediae)
within globular “ cysts ” within ciliated ‘‘ mother sporocysts ” (rediae)
are also ciliated and bear eye-spots is indeed puzzling. I n addition to
finding these unusual sporocysts ” in Cardium edule, Nicoll reported
that they also encyst in the foot of Mytilus edulis and Mactra stultorum.
Body elongate oval, with pointed anterior end and
blunt posterior end, covered with cilia, 0.2-0.8 mm long x 0.38 mm at
greatest width ; with two crescentric eye-spots near anterior end ;
small pharynx anteromedial to eye-spots ; with six to eight globular
‘‘ cysts ” in body; with each mature “ cyst ” containing two to four
‘‘ daughter sporocysts ” (rediae) ; immature “ cysts ” generally situated
near body wall at anterior end of ‘‘ mother sporocyst ” (rediae) ; fully
formed “ daughter sporocysts ” (rediae) within “ cyst ” appear as
miniature “ mother sporocysts ” (rediae), including two eye-spots and
cilia.
Other information. From Nicoll’s description it would appear that a
second miracidial generation is formed within the “ cysts ” found in the
parenchyma of mother rediae which in turn most probably represent
miracidia which have not lost their ciliated coat. This most unusual
succession of generations may represent a misinterpretation on Nicoll’s
part, but then it may represent an aberrant life cycle pattern somewhat
Description.
253
anterior one-third of body; two testicular anlagen globular, one on
each side of pyriform structure (identity unknown) , behind ventral
sucker; duct leading from pyriform structure to cirrus situated immediately anterior to ventral sucker ; excretory vesicle Y-shaped with
arms extending to between caecal tips and ventral sucker, stem pearshaped.
Other information. Nothing else is known about C. tenuans. Although
Cole appeared to be convinced that this parasite caused the death of
Mytilus edulis, in my opinion this hypothesis should be accepted with
caution since he only found six out of 300-400 dead mussels to be
infected.
40. Unidentified ‘ I Sporocyst ” of Nicoll, 1906. (Fig. 167)
(Taxonomic position undetermined)
During an examination for parasites in Cardium edule from the
vicinity of St. Andrews, Scotland, Nicoll(1906b) reported the occurrence
of a most unusual “ sporocyst ” in the hepatopancreas and on the
adjacent intestine. From his description, which is summarized below,
it would appear that he had found miracidia in the process of metamorphosing into rediae rather than sporocysts since it contains a
pharynx ; however, the fact that the “ daughter sporocysts ” (rediae)
within globular “ cysts ” within ciliated ‘‘ mother sporocysts ” (rediae)
are also ciliated and bear eye-spots is indeed puzzling. I n addition to
finding these unusual sporocysts ” in Cardium edule, Nicoll reported
that they also encyst in the foot of Mytilus edulis and Mactra stultorum.
Body elongate oval, with pointed anterior end and
blunt posterior end, covered with cilia, 0.2-0.8 mm long x 0.38 mm at
greatest width ; with two crescentric eye-spots near anterior end ;
small pharynx anteromedial to eye-spots ; with six to eight globular
‘‘ cysts ” in body; with each mature “ cyst ” containing two to four
‘‘ daughter sporocysts ” (rediae) ; immature “ cysts ” generally situated
near body wall at anterior end of ‘‘ mother sporocyst ” (rediae) ; fully
formed “ daughter sporocysts ” (rediae) within “ cyst ” appear as
miniature “ mother sporocysts ” (rediae), including two eye-spots and
cilia.
Other information. From Nicoll’s description it would appear that a
second miracidial generation is formed within the “ cysts ” found in the
parenchyma of mother rediae which in turn most probably represent
miracidia which have not lost their ciliated coat. This most unusual
succession of generations may represent a misinterpretation on Nicoll’s
part, but then it may represent an aberrant life cycle pattern somewhat
Description.