508 ENTQZOA. 



FASCIOLA, Lin. 



Which may be subdivided according to the number and position of their 

 organs of adhesion. 



DISTOMA. 



Here there is a sucker at the anterior extremity of the mouth, and a cup, 

 a little posterior to it, on the venter. The species are very numerous, and 

 some are found even in the plaited membrane of the eyes of certain Birds. 

 Others, however, appear to inhabit fresh and salt water. The most cele- 

 brated is 



D. hepatica. It is very common in the hepatic vessels of Sheep, but is 

 also found in those of various other lluminantia, and of the Hog, Horse, and 

 even of Man. Its form is that of a small oval leaf, pointed posteriorly, 

 with a narrowed portion anteriorly, at the end of which is the first sucker, 

 which communicates with a sort of esophagus, from which arise canals that 

 ramify throughout the body, conveying the bile on which this animal feeds. 



The species that infest Sheep become greatly multiplied when they graze 

 in low and wet grounds, rendering them dropsical, and finally killing them. 



There are several other genera* 



FAMILY III. 



T^NIOIDEA, 



In our third family of parenchymatous Intestinal Worms, we place 

 all those species in which the head is provided with two or four 

 suckers placed around its middle, which is itself sometimes marked 

 with a pore, and sometimes furnished with a little proboscis, naked 

 or armed with spines. Sometimes there are four little trunks thus 

 armed. 



The most numerous genus is 



TJENIA, Lin. 



The body of the Tape-worm is often excessively elongated, flat, composed 

 of joints more or less distinctly marked, and narrowed anteriorly, where we 

 generally find a square head hollowed by four small stickers. 



Observers have thought that they could perceive canals which arose 

 from these suckers, and crept along the margin of the joints of the body. 

 Each of the latter has one or two pores differently situated, according to the 

 species, which appear .to be the orifices of ovaries that are placed in the 

 thickness of the joints, where they are sometimes simple, and at others 

 ramous. The Taeniae are among the most cruel enemies of the animals in 

 which they are developed, and which are apparently exhausted by them. 



