100 HAROLD HEATH. 



attached and was put in communication with the exterior by a 

 slit-like aperture 2 mm. long. The body is subglobular in 

 form, distinctly bilateral, light yellow in color and measures 14 

 mm. by 1 1 mm. The external opening, communicating with 

 the exterior through the aperture in the arm of the host, is in 

 the mid line and is surrounded by prominent lips. These last 

 named structures are covered with a firm cuticle produced into 

 16 pairs of interlocking teeth (Fig. 6, PI. L). 



An examination of Fig. i, PI. I., will disclose the fact that the 

 body proper, containing practically all the organs except the 

 female reproductive gland, is overgrown by a great fold attached 

 to the front end of the body, but elsewhere separated from it by 

 a narrow slit-like space which communicates with the above men- 

 tioned fissure-like opening guarded by teeth. Anteriorly the 

 ventral surface of the body is developed into a snout-like projec- 

 tion bearing the mouth opening and a small pair of tentacles 

 (Fig. i). More posteriorly the ventral surface, corresponding 

 to the foot of free living forms, is somewhat flattened but lacks 

 the usual high ciliated epithelium and gland cells. Still farther 

 back the peculiar kidney forms the ventral surface behind which 

 is the rectum borne on a papilla-like elevation. Some of these 

 characters and others to be mentioned indicate distinctly gastro- 

 pod relationships which have been retained in spite of parasitic 

 habits. 



The entire surface of the body is covered with a cuticular layer 

 usually well developed on the ventral surface over the lobe-like 

 projections shown in Fig. 8, PI. I. In this last named region it 

 becomes developed into numerous small papillae each of which 

 is penetrated by what is probably a nerve fiber (Fig. 7, PI. I.). 

 Within the animal the layer is much thinner and over the respira- 

 tory papillae {p) and the adjacent regions is provided with numer- 

 ous slender and apparently solid, hair-like processes. 



The hypodermal layer consists of flattened cells, with large 

 nuclei, separated at many points to allow muscle fibers to attach 

 directly to the overlying cuticle. In addition there are many 

 bipolar cells, one fiber passing distally into the above mentioned 

 cuticular papillae the other becoming lost in the subjacent tissue. 



The mouth opening is situated upon the summit of a well-defined 



