No. 2.] STRUCTURE OF TWO FISH TAPEWORMS. 343 



as a dark line in transverse sections (PI. XVI, Fig. 11, m.c.ct.). 

 Beneath this layer is a row of dots, which mark the sections 

 of longitudinal muscle fibers (PI. XVI, Fig. 11, m.l.ct.). In 

 frontal sections, cut somewhat obliquely, these subcuticular 

 muscles can be best observed. Here the transverse fibers are 

 seen to be thick and in the form of a fibrous mat, while the 

 longitudinal fibers are separate and cross the others at right 

 angles. 



The subcuticular cells are slightly pyriform, with a large 

 nucleus (PI. XVI, Fig. 11, sb.c). None of them are closer to 

 the muscle layers than .0075 mm., but each sends one or more 

 processes into the subcuticular muscle layers, beyond which 

 they can no longer be traced. 



The parenchyma cells are irregular in shape and rather 

 closely packed, presenting the appearance of a fine meshwork 

 with nuclei in the spaces. Scattered throughout the paren- 

 chyma are numerous calcareous bodies of various oval shapes, 

 none larger than .007 mm. in diameter (PI. XVI, Fig. 16, ca.). 



Miisailatiire. — The longitudinal body muscles are very 

 prominent ; they are arranged in irregular bundles, from fifty 

 to sixty in all, which vary in thickness from .05 mm. to a 

 fourth that size (PI. XVI, Fig. 16, l.m). 



As the scolex is approached, the bundles become smaller 

 and the fibers are not so closely compacted, many of them 

 leaving the bundles and extending separately through the 

 parenchyma. In the scolex the fibers are no longer arranged 

 in bundles, but penetrate the parenchyma as scattered fibers. 



Within these bundles is another muscle layer. In trans- 

 verse section that portion of the proglottis which is filled with 

 sexual organs is seen to be bounded by a thin sheet of wavy 

 fibers (PI. XVI, Fig. 16, vix). From the sheet single fibers 

 dip down irregularly and pass between the organs. The ends 

 of the fibers are coiled like a corkscrew. Other fibers go 

 outward between the large muscle bundles and take a wavy 

 irregular course toward the subcuticular cells. In the scolex 

 these fibers show a radiate arrangement (PL XVI, Fig. 3, 7n.c.), 

 and transverse sections in this region show the diagonal fibers 

 crossing: at the center. 



