No. 516] THE CUTICULA OF CESTODES 



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never in trematodes— and epithelial cells, without which it 

 is not likely that any one would ever have thought of this 

 epithelial theory. These cells in cestodes are, as we have 

 seen, usually elongated and spindle-shaped and lie paral- 

 lel to one another, so that they look a good deal like iso- 

 lated epithelial cells. But it must also be noticed (Fig. 

 1) that all the other cellular elements of the peripheral 

 region— the parenchyma cells, the gland cells and the 

 sense cells— are also elongated and spindle-shaped and lie 

 parallel to one another and to the subcuticular cells. Ap- 



parently some common cause, in the nature of a tension 

 in a dorsoventral direction, has acted upon the entire 

 peripheral region of the body of the worm, distorting 

 more or less all the structures in it. Leuckart (1886) has 

 suggested— and Leuckart 's suggestions are always fruit- 

 ful—that this spindle form is due to the action of the 

 powerful dorsoventral muscles which run across the 



