358 BENEDICT. [Vol. XVI. 



identical in shape in different individuals, varying in form from 

 nearly square to an oblong in which the length is twice the 

 breadth. The greatest breadth of the body comes in the next 

 to the last proglottis. The posterior proglottis makes a gradual 

 taper toward the posterior end, which is smoothly rounded. 

 The excretory pore can be seen at the tip as a cup-shaped 

 indentation. 



Anatomical and Histological Structure. 



Cuticula. — The cuticula is very delicate, .0035 mm. in thick- 

 ness ; the external layer presents a very rough appearance (PI. 

 XVI, Fig. 29, ct\). It takes stain more deeply than the other 

 layer. There is no smooth outline on the exterior, as drawn 

 by Kraemer. What he pictures as a homogeneous layer, pene- 

 trated by perpendicular canals, is in reality a ragged, exceedingly 

 irregular layer, with clefts and breaks reaching down to the 

 next layer. Its appearance suggests the sloughing off of the 

 cuticula. The layer of cuticula beneath this is .002 mm. thick, 

 and stains lightly (PI. XVI, Fig. 29, ct). 



Beneath the cuticula is a layer of circular muscles .001 mm. 

 thick, and within these is a layer of longitudinal muscles, which 

 in cross-sections shows as a row of dots between the outer ends 

 of the cell processes of the next layer (PI. XVI, Fig. 29, 

 m.l.ct. and m.c.ct). 



The subcuticular cell layer is very prominent, having a thick- 

 ness of ,025 mm, (PI, XVI, Fig, 29, sb.c). The cells are 

 narrow, fusiform, with long delicate processes on the distal 

 ends. The subcuticular cell layer in P . filicollis is much more 

 prominent than in P. ambloplitis. In transverse sections the 

 cells form a band, over half the thickness of the dermo-mus- 

 cular sac in P. filicollis, while in P. ambloplitis the band only 

 constitutes one-fifth of the thickness of the dermo-muscular 

 sac (PI. XVI, Figs, 16 and 23, sb.c). 



The parenchyma is very open and loose in texture, looking 

 like a coarse, irregular meshwork. Muscular fibers are scat- 

 tered throughout it, extending in a transverse direction. In the 

 area enclosed by the longitudinal body muscles the parenchyma 



