3s4
N. BALAKRISHNAN NAIR AND 31. SARASWATIIY
in Bankia gouldi and Teredo navalis but persists in Teredo dilatata.
Sigerfoos also noted a duct leading to the exterior and opening at the
side of the mouth on the ventral side of the velum in the larvae. The
opening of the duct into the oesophagus in Teredo furcifera suggests
several possibilities concerning the function of this gland. Whether
these glands have any role in the digestion of cellulose has to be
ascertained on the basis of histochemical and physiological tests. In
Teredora princesae the umbonal portion of this gland is well developed
(Saraswathy and Nair, 1971). That part of the gland in the gill laminae,
especially around the gill axis, in N . hedleyi, B. gouldi and B. indica is
apparently not represented. The ducts of Deshayes in the afferent
branchial vein (Fig. 23) contain a special development of this gland with
minute filamentous structures and also a few well defined rounded
bodies containing granular material. Probably this represents the
glandular part reported by Deshayes within the afferent branchial
veins. Anteriorly beneath the umbo there is a massive development of this organ which is continuous with the portion contained
within the afferent branchial veins. This shows that all are essentially
parts of the same structure as suggested by Sigerfoos. Deshayes considered that the secretion from umbonal glands softened the wood and
that those in the gill served as a source of nourishment for the viviparous embryos.
The function of these peculiar structures unique in the Teredinidae
is unknown. Whether they are concerned with the elaboration of some
internal secretion for whose formation the presence of both blood and
water is necessary as suggested by Sigerfoos, though reasonable, remains to be investigated. The nutritive function suggested by Deshayes
is not convincing since they are present in oviparous species such as
Banlcia gouldi, B. indica and Nausitora hedleyi.
10. Circulatory system
Menegaux (1890) described the circulatory system in Teredo navalis
Sellius (Linne), T . norvegica Spengler and T . pedicellata Quatrefages.
The first adequate account was given by Sigerfoos (1908) for both the
young and adult Banlciagouldi, even though as early as 1684, Redi noted
the possession of a heart which is discernible with the naked eye in
shipworms. Sigerfoos observed the same fundamental plan in the three
species B. gouldi, T . navalis and T . dilatata, though in the last named,
because of the more posterior position of the gills, the heart-especially
the aorta-like part of the ventricle-is more elongated.
The heart lies in a tubular pericardium on the apparently dorsal,
but morphologically ventral side of the intestine. It varies considerably
N. BALAKRISHNAN NAIR AND 31. SARASWATIIY
in Bankia gouldi and Teredo navalis but persists in Teredo dilatata.
Sigerfoos also noted a duct leading to the exterior and opening at the
side of the mouth on the ventral side of the velum in the larvae. The
opening of the duct into the oesophagus in Teredo furcifera suggests
several possibilities concerning the function of this gland. Whether
these glands have any role in the digestion of cellulose has to be
ascertained on the basis of histochemical and physiological tests. In
Teredora princesae the umbonal portion of this gland is well developed
(Saraswathy and Nair, 1971). That part of the gland in the gill laminae,
especially around the gill axis, in N . hedleyi, B. gouldi and B. indica is
apparently not represented. The ducts of Deshayes in the afferent
branchial vein (Fig. 23) contain a special development of this gland with
minute filamentous structures and also a few well defined rounded
bodies containing granular material. Probably this represents the
glandular part reported by Deshayes within the afferent branchial
veins. Anteriorly beneath the umbo there is a massive development of this organ which is continuous with the portion contained
within the afferent branchial veins. This shows that all are essentially
parts of the same structure as suggested by Sigerfoos. Deshayes considered that the secretion from umbonal glands softened the wood and
that those in the gill served as a source of nourishment for the viviparous embryos.
The function of these peculiar structures unique in the Teredinidae
is unknown. Whether they are concerned with the elaboration of some
internal secretion for whose formation the presence of both blood and
water is necessary as suggested by Sigerfoos, though reasonable, remains to be investigated. The nutritive function suggested by Deshayes
is not convincing since they are present in oviparous species such as
Banlcia gouldi, B. indica and Nausitora hedleyi.
10. Circulatory system
Menegaux (1890) described the circulatory system in Teredo navalis
Sellius (Linne), T . norvegica Spengler and T . pedicellata Quatrefages.
The first adequate account was given by Sigerfoos (1908) for both the
young and adult Banlciagouldi, even though as early as 1684, Redi noted
the possession of a heart which is discernible with the naked eye in
shipworms. Sigerfoos observed the same fundamental plan in the three
species B. gouldi, T . navalis and T . dilatata, though in the last named,
because of the more posterior position of the gills, the heart-especially
the aorta-like part of the ventricle-is more elongated.
The heart lies in a tubular pericardium on the apparently dorsal,
but morphologically ventral side of the intestine. It varies considerably