G9 



part of the stomach is occupied by the opening of a larfje , 

 conical diverticulum which is median in position, the 

 sheath of the crystalline style (C.^j. j'igs. 2,24). Its 

 walls are composed of the larr;e, coarsely granular, dense- 

 ly ciliated cells characteristic of this structure, ex- 

 cept at the blind end, where the cells are smaller, more 

 finely granular and non-ciliated, (fig. 24). 



The alimentary canal of the larva is interesting be- 

 cause of the advanced development of some parts and the 

 retarded development of otliers. The liver has advanced 

 but little in form beyond a stage reached two or three 

 days after hatching. On the other hand, the caecum of the 

 stomach, which is peculiar to the menbers of the Pholada- 

 rea, is already present as a rudiment, although it is not 

 to become ftmctional till after the adoption of the life 

 in the v/ood. 



As the lai*va develops into the "Ship-worm" , the size 

 and relations of the parts of the alimentary canal change 

 greatly. The oesophagus becomes, in the adult, very short 

 in comparison with other parts (fig. 10). The stomach 

 elongates posteriorly more and more (figs. 4,7,:").) till 

 in the adult it projects far beyond the posterior adductor 

 and forms a long cylindrical tube (fig. 10). As is well 



