The structure and function of the liver of Teredo, the shipworm

(i) The liver of the Teredinidae is shown to consist of three regions, the physiological relations of which have not been fully elucidated:

A. A “digestive” region in which the cells are phagocytic and nearly always contain minute fragments of wood. The phagocytic cells are mostly free in the lumen of the liver which also contains enormous quantities of wood. They are probably derived from the epithelium of the liver, which is also often phagocytic, containing wood fragments. Where this is not so the epithelium is ciliated internally.

B. In other lobules the liver wall is thickened locally and the lumen contains ciliated cells and cell aggregates, which are colourless, with small granular inclusions, and never contain wood.

C. An “excretory” region consisting of cells, also typically ciliated, containing large quantities of highly refringent, resistant granules whose chemical nature is not known but which are probably excretory. The lumen contains similar free cells.

(2) Glycogen has not been demonstrated in the liver but occurs in large quantities in the mantle and elsewhere. Fat globules are found in the epithelium of region A.

(3) The stomach, coecum and liver lumen contains no other recognisable organic material beside wood and only very occasional diatoms are found in the intestine. The gills of Teredo, though much modified, collect solid particles by ciliary action and forward them to the mouth. When kept in a suspension of Indian ink, the ink is found in the gut and the liver and even in the liver cells. In natural conditions material, which could have been so collected, is not recognised in those situations. Other evidence is given to indicate the shipworm's practical independence of plankton organisms.