MANUAL OF NATUKAL HISTOKY. 359 



11. Family— Horn-like Corals (Cornulariidse) Poly- 

 pary horny, fixed, composed of small horn- 

 like conical tubes, erect, each containing a 

 single terminal solitary polyp, with eight 

 dentato-pinnate tentacles. 



PARENCHYMATOUS-PARASITES. 



The Parenchymatous Worms of Cuvier, or the 

 Sterelmintha of Owen, are much more simple in 

 their structure than the Cavitary or Ccelelminthous 

 Parasites, their intestinal canal not being provided 

 with distinct walls, and their nervous system being 

 very faintly developed. They are nourished by the 

 juices of other animals, within whose bodies they 

 take up their abode. On this account their diges- 

 tive organs are very simple ; there is no trace of 

 locomotive organs or even of muscles, and the senses 

 are reduced to a single diffused and general sense of 

 touch. 



These parasitic worms are found infesting man 

 and the lower animals, inhabiting various tissues 

 and parts of the body, as the eyes of fishes, the 

 brains of sheep, the muscles, the air-passages, the 

 liver, the blood, and the alimentary canal. Among 

 the Cystiform families we find the Hydatids, which 

 resemble transparent bladders filled with fluid, with 

 mouths at the small end furnished with little hooks 

 and suckers. The common species, sometimes found 

 in man, is the Cysticercus tenuicollis ; another 



