117 



In places where the cells are separated owing to expansion of the 

 worm, the subcuticula is seen to consist of elongated cells, rich in proto- 

 plasm, standing at right angles to the cuticula ; these cells are in contact 

 with the innermost cuticula layer by three, four, or more processes, which 

 are again often branched before reaching the cuticula. These processes 

 appear occasionally to form anastomoses with processes from the same or 

 other cells, before inserting in the cuticula. The proximal end of the 

 cell terminates in a single elongate process, which is continued into a long 

 fibrilla ; these fibrillae can sometimes be traced continuously through the 

 ring-muscle into the middle layer of the worm and from thence to the 

 cuticula of the opposite side, sometimes interrupted on their course by 

 the spindle-shaped cells belonging to the transverse-muscle system. 



The fibrillae of several adjacent cells appear to close together into 

 definite bundles before penetrating the longitudinal muscles ; this is best 

 seen on more contracted portions. 



The subcuticula cells appear to have traces of a membrane, are very 

 distinctly outlined, and their plasma appears to be slightly denser along 

 the walls of the cells. 



The nuclei of the subcuticula cells consist of small vesicles ; the 

 membrane surrounding the nucleus stains quite distinctly ; each nucleus 

 contains several round chromatine bodies, often five or six in addition to 

 the nucleolus, which is about twice the size of the chromatine bodies. 



The measurement of a few subcuticular cells is (Zenker's solution — 

 haematoxylin orange — 20 cm. from scolex) : — 



(a) Total length of cell from 



insertion in cuticula to 



attachment to fibrilla . . 57 f 42, f^ 36 1^ 42 f 60 1^ 51 f* 



(b) Grreatest width of same cell 3i^4-5i^ 6 f^ 4i« 4i« 4^ 



(c) Length of nucleus .. .. 6i« 6/« 5/" 5^5f'6:« 



(d) Breadth of nucleus .. 3 1« 4-5/* 4-5:" 4i« if^ 3/^ 

 Only such cells were measured whose insertion in the cuticula and 



attachment to the fibrilla could be made out. The attachment to the 

 fibrilla is only able to be found in cells lying entirely in the plane of the 

 section. 



Between the just described subcuticula cells and the cuticula, two 

 layers of muscle fibrillae are to be found running parallel to the cuticula. 



The outermost of these runs horizontally and forms an outer ring 

 muscle layer ; the inner one runs at right angles to it in the direction of 

 the long axis of the worm. The outermost longitudinal fibres pass between 

 the circular fibres. These systems are best studied on sections parallel to 

 the surface of the cuticula, but can be made out also on transverse sections. 



Calcareous Corpuscles. 



Stilesia centrifunctata does not seem to possess any calcareous bodies. 



