THE BlOLOCY O F WOOD-BORING TEltYUINIU MOLLUSCS
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tent shows a slight but gradual decrease with increase in body weight
(Sreenivasan, 1961).
In Nausitora hedleyi the non-protein nitrogen content varies during
the different times of the year. The difference is marked during the
period June-October when low values prevail. Giese and Araki (1962)
detected the presence of a surprisingly high percentage of non-protein
FIG. 44. Curves showing the variat,ions in glycogen (A), and protein (B), content of
Nausitora hedleyi in relation to increase in weight of the body.
nitrogen in the mantle of Katherina and the large amount of nonprotein nitrogen present in the testes was attributed to accumulation
of nucleic acid in the sperm. They noticed no change in the non-protein
nitrogen content in these chitons during the breeding cycle. In the
light of these observations, the following explanation for the fall in nonprotein nitrogen during the breeding season of Nausitora hedleyi may
be given. During the non-breeding season, the non-protein nitrogen