1924] Lazier: Morphology of Digestive Trad of Teredo navalis 467 



SUMMARY 



1. The digestive trad of Teredo navalis Linn, is well developed, 

 and although highly specialized, it retains the essential features of 

 the typical lamellibranch system. 



2. The dorsal labial palps are small hut distinct; the ventral pair 

 are reduced but still functional. 



■i. The usual ciliary mechanism for the capture and ingestion of 

 plankton and for the disposal of excess sediment taken from the water 

 is present in a slightly modified form, with additional ciliated tracts 

 for the ingestion of the wood fibers obtained by boring. 



4. The stomach is long and subcylindrieal. 



5. The digestive glands are highly developed. The posterior one 

 communicates with the stomach by a single orifice, but consists (if 

 two kinds of secretory tissue 



6. The large caecum characteristic of the Teredinidae is present. 

 A large artery carries blood directly from the heart to the caecal 

 typhlosole. Tile interior of the caecum is not ciliated, but food is 

 apparently moved by muscular activity. 



7. The crystalline style and its related mechanism are similar to 

 that of many other lamellibranchs. 



8. A small, pointed dorsal caecum is present. 



9. The stomach contains two typhlosoles, one of which is continuous 

 with that of the intestine. 



10. The cilia in the stomach are confined to certain limited tracts. 



11. The intestine is relatively short and contains a large coiled 

 typhlosole near the stomach. Throughout the remainder of its length 

 the typhlosole is absent. 



12. The whole digestive tract is bathed in blood carried in sinuses. 

 The typhlosoles have a direct arterial supply. 



13. Comparisons with descriptions by other authors indicate wide 

 differences in the gross structure of the alimentary tract in various 

 species of Teredinidae. Such differences may prove of taxonomic 

 value. 



14. Differential staining of wood fibers in the caecum and in the 

 intestine is evident of the digestion of cellulose. 



