No. 3.] STUDY OF STENOSTOMA LEUCOPS O. SCHM. 271 



The muscular wall is made up of longitudinal and circular 

 fibres which run at right angles to each other. The longitu- 

 dinal fibres are next to the ciliated cells. In a cross-section the 

 longitudinal fibres (Fig. 6, L.M.) are oval, their greatest diam- 

 eter being perpendicular to a radius of the pharynx drawn to 

 them These fibres are .75 /x broad and .5 /x thick. 



The circular fibres (Figs. 7 and 8, CM.) are also oval in cross- 

 section and somewhat larger than the longitudinal fibres. They 

 are i /x in breadth and .5 /^ in thickness. Their greatest diam- 

 eter is parallel to a radius of the pharynx drawn to them. The 

 circular fibres are more plentiful than the longitudinal. The 

 longitudinal fibres, when the pharynx is in its normal shape, are 

 separated from one another by an interval equal to double their 

 own width, while the circular fibres are not further apart than 

 the length of their smallest diameter. No nuclei were discov- 

 ered in these fibres. 



The inner layer of ciliated cells is made up of a single tier 

 of cells These cells (Fig. 6) are club-shaped, with their nar- 

 row ends attached to the muscular layer. They range from 3 /^ 

 to 3 5 /. in length, and are i ^ in width. From their large dis- 

 tal ends extremely long and slender cilia {C) project into the 

 lumen of the pharynx and nearly fill it. The cilia are from 7 /^ 

 to 9 /. in length, -nearly three times as long as the cells which 



bear them. 



There is a distinct line of demarcation between the anterior 

 end of the pharynx and the cone-shaped depression of the integ- 

 ument This is noticeable both in the ciliated cells and the 

 muscular layer. As was before stated, the ciliated cells linmg 

 the depression are like those of the integument. These cells 

 grow o-radually smaller from the outside toward the pharynx. 

 At the point X (Fig. 5) they cease to be visible, and immedi- 

 ately beyond that point the very much larger pharyngeal cells, 

 which are provided with much longer cilia, may be seen occu- 

 pying the same position relative to the muscular wall. 



There is also a difference in the relation of the fibres of 

 the muscular layer to the epithelial cells of the two regions. 

 As was stated above, the longitudinal fibres of the pharynx he 

 next to the epithelial cells, while in the cone-shaped depression 

 the circular muscle fibres occupy that position. The circular 

 and lono-itudinal fibres of both the pharynx and the depression 



