374
N. BALAKRISHNAN NAIR AND M. SARASWATHY
lies the second group, The posterior and by far the largest mass is
distinguishable into a large more dorsal right half and a small left half.
The former is brownish green and lies on the right side of the posterior
part of the stomach while the latter is fawn-coloured and composed of
few tubules containing particles of wood, a condition similar to what
Lazier (1924) found in Teredo navulis. The condition in Nuusitoru
hedleyi (Saraswathy and Nair, 1971) is slightly different. The set of
tubules forming the ventral " liver " noticed in Teredo (Lazier, Zoc. cit.)
and Bunkiu (Nair, 1957a) is not distinguishable in Nuusitoru hedleyi.
The major part of the diverticula forms a large, compact mass closely
attached to the stomach and the anterior part of the caecum. Here, the
diverticula are disposed chiefly in the lateral and ventral regions of the
stomach. The whole mass shows a characteristic appearance with a
comparatively small, deeply pigmented region on the right side which
represents the region of the unspecialized part of the digestive diverticula. The relative proportions of the two regions are also different. In
Nazcsitora hedleyi there is a pronounced development of the lightly pigmented specialized region compared with the unspecialized part which
is represented only as a small mass on the right side.
The main passages through which the specialized digestive diverticula bommunicate with the stomach are apparently devoid of any
special device aiding in the selection, acceptance or rejection of
material. However, Potts (1923) noticed in fresh material of Teredo
that the cells of the tubules of the specialized region carry long, easily
retractile cilia which beat with a languid motion. Probably particles
of wood from the stomach and caecum are drawn into these diverticula
partly through the movements of the anterior part of the body while
boring. The ducts of the unspecialized region of the digestive diverticula are lined by tall, columnar, ciliated cells with centrally placed
nuclei. Yonge (1926) has shown that the digestive diverticula are not
secretory. Nair (1957s) has observed the occurrence of amoeboid cells
ingesting wood fragments in the specialized part of the digestive diverticula.
A correlation between the development of the specialized part of the
digestive diverticula and the elaboration of the caecum (=appendix) is
also evident in the Teredinidae. I n Teredoru and Nototeredo where the
caecum is less developed the specialized part is absent while in Nuusitoru
where the caecum is most fully developed the specialized part of the
digestive diverticula is proportionately large. However, the apparent
relationship between the development of the specialized digestive
diverticula and the ability to digest cellulose has yet to be clearly
established.
N. BALAKRISHNAN NAIR AND M. SARASWATHY
lies the second group, The posterior and by far the largest mass is
distinguishable into a large more dorsal right half and a small left half.
The former is brownish green and lies on the right side of the posterior
part of the stomach while the latter is fawn-coloured and composed of
few tubules containing particles of wood, a condition similar to what
Lazier (1924) found in Teredo navulis. The condition in Nuusitoru
hedleyi (Saraswathy and Nair, 1971) is slightly different. The set of
tubules forming the ventral " liver " noticed in Teredo (Lazier, Zoc. cit.)
and Bunkiu (Nair, 1957a) is not distinguishable in Nuusitoru hedleyi.
The major part of the diverticula forms a large, compact mass closely
attached to the stomach and the anterior part of the caecum. Here, the
diverticula are disposed chiefly in the lateral and ventral regions of the
stomach. The whole mass shows a characteristic appearance with a
comparatively small, deeply pigmented region on the right side which
represents the region of the unspecialized part of the digestive diverticula. The relative proportions of the two regions are also different. In
Nazcsitora hedleyi there is a pronounced development of the lightly pigmented specialized region compared with the unspecialized part which
is represented only as a small mass on the right side.
The main passages through which the specialized digestive diverticula bommunicate with the stomach are apparently devoid of any
special device aiding in the selection, acceptance or rejection of
material. However, Potts (1923) noticed in fresh material of Teredo
that the cells of the tubules of the specialized region carry long, easily
retractile cilia which beat with a languid motion. Probably particles
of wood from the stomach and caecum are drawn into these diverticula
partly through the movements of the anterior part of the body while
boring. The ducts of the unspecialized region of the digestive diverticula are lined by tall, columnar, ciliated cells with centrally placed
nuclei. Yonge (1926) has shown that the digestive diverticula are not
secretory. Nair (1957s) has observed the occurrence of amoeboid cells
ingesting wood fragments in the specialized part of the digestive diverticula.
A correlation between the development of the specialized part of the
digestive diverticula and the elaboration of the caecum (=appendix) is
also evident in the Teredinidae. I n Teredoru and Nototeredo where the
caecum is less developed the specialized part is absent while in Nuusitoru
where the caecum is most fully developed the specialized part of the
digestive diverticula is proportionately large. However, the apparent
relationship between the development of the specialized digestive
diverticula and the ability to digest cellulose has yet to be clearly
established.