2 2 Charles GELDERD 



It is formed of chitinous folds inserted laterally, S, s, SJ, running over 

 an under cavity which contains'the pyloric pièces S,, S^. 



The lower folds SJ are capable of overlapping and in that case ail 

 communication between the upper passage and the cavity below is shut 

 off. We may mention hère an important différence between the Schizopoda 

 and the Edriophthalmia. In the latter, corresponding folds are found, 

 but much less developed than in the Schizopoda. They never overlap. 

 Nevertheless, there is a tendancy, especially in Gammariis, towards the 

 formation of a cylindrical passage. 



With this gênerai description of the posterior cavity of the stomach, 

 we shall now examine the sections, fig. 3, 7, 8, 9, Il to 19. 



FiG. 8 and 9 give a good idea of the connection between the pièces S^ 

 and the pièces of the pyloric cavity. 



Fig. 8 is a section in the vertical plane including a portion of one of 

 the pièces S,. 



The epithelial lower and upper borders are seen to converge at the 

 entrance to the pyloric chamber, where they join the folds l.v\, bi\, which 

 are the Connecting arms between S^ and the folds S^s, SJ, fig. 8, 9. 



In FIG. 8 a muscular band is seen, i7ic, which is but one of several cir- 

 cular muscles which surround the passage between the two cavities of the 

 stomach. 



The lower arm bi-^ is inserted in the form of an articulation behind the 

 spur-like terminal portion of the ridge c which runs along the cardiac 

 chamber between the plates S, fig. 3, 9. 



This free insertion enables ail the pièces to move freely during the 

 masticating process. 



We hâve already seen the horizontal aspect of the arms and folds bi\, 

 b}\, 5,5, 5,zin fig. il, 12. 



The arms bi\, bi\ and folds S^s, SJ are thin chitinous folds formed 

 by a raised epithelium, fig. 7, 15. 



The upper borders of the folds are fringed with sharp spines which 

 meet in the médian plane when the passage is closed, fig. 7. 



The lower borders, fringed also with spines, are capable of overlapping, 

 fig, 7, 12. 



In FIG. 15, which is a transverse section through the pyloric chamber 

 at the level indicated by the same number in fig. 3, the folds hâve been 

 withdrawn by the agency of muscles which surround the pyloric chamber 

 inserting themselves in the epithelium at the level of the upper fold 5,5. 



