PARASITES FOUND IN EHHINDS ESOULENTUS, L. 288 



some cases the latter is produced into a small papilla caused 

 by the evagination of the penis. 



The mouth leads into a well-marked sucker-like pharynx. 

 It is situated on the ventral surface in the middle line, about 

 one eighth of the body-length from the anterior end of the 

 animal. The opening of the vas deferens, the vagina, and 

 the uterus are all at the posterior end of the bod\^, and open 

 by a common pore (figs. 4 and 5). 



There are no tentacles, or papillas, or hooks, or spines, and 

 as far as I could obser^^e no skiii-glauds. 



Histology. — The whole body is covered with a thin but 

 distinct cuticle of uniform thickness (fig. 6). This is continued 

 into the moutli and genital openings, but soon disappears. 

 Externally this cuticle bears numerous small processes, very 

 minute, but sufficient to give a rough appearance to the out- 

 side surface under a high power of the microscope. These 

 are almost certainly the cilia described by all authors who 

 have observed the animal alive. 



The cuticle is secreted by a single layer of ectoderm cells 

 with large, clear, spherical nuclei (fig. G). In some sections 

 these ectoderm cells showed fairlj^ definite cell limits, and in 

 that case each cell was about as broad as it was long; in 

 other cases the limits of the cell could only be guessed b}^ 

 observing the nuclei placed at regular intervals. In all the 

 specimens I cut the ectoderm of the dorsal and ventral 

 surfaces had separattul from tlie subjacent tissues, leavino- a 

 considerable space, but it had retained its normal position 

 along the edges of the animal. 



Beneath the layer of ectoderm cells is a basement mem- 

 brane, which seems, however, to belong rather to the under- 

 lying parenchymatous cells than to the ectoderm ; it gives a 

 smooth and clearly defined outline to the body where the 

 ectoderm has broken loose fi'om it. 



The muscidar system described by some authors was not 

 visible in my sections. 



The parenchyma of the body presented different appearances 

 in accordance with the different state of preservation of the 



