70 



known, the wood -^rated away in boring, is invested and 

 stored in the caecum of the stomach. Even bel'oro the in- 

 gestion of t'no wood berins , the caeciim projects into the 

 foot as a large hollow vesicle, lined by clear, ciliated 

 cells. But, as soon as v;ood is ingested, it enlarges rap- 

 idly and soon forms the largest part of tlie alimentary 

 canal (figs. 4,7,10 Ce.). V/ith its increase in size, it 

 comes to leave the posterior end of the stomach, and 

 crowds the sheath of the crystalline stylo to the left 

 side (figs. 4,7,10). In young specimens, the caec^um occu- 

 pies almost the whole mass of the foot, and its blind end 

 points forwards (figs. 4,7). As the visceral mass elon- 

 gates, the caecum is gradually dravm backwards, till in 

 the adult, it forms a very long c^'lindrical tube, stretch- 

 ing to the posterior end of tlie visceral mass (fig, 10 (-e.) 

 In "nhip-worms" that are boring and grov/ing, the caecum is 

 always completely filled with ingested particles of v;ood. 

 The scarcity of diatoms and other food materials seems to 

 indicate that in the "Ship-v/orm" , boring and ingestion of 

 wood, and ingestion of food alternate , and that, when 

 feeding, tlie food is guided into the intestine; and when 

 boring, into the caecum. The caecum, then, is a long, 



