ENTOZOA. 403 



canal resembles that of the Bonellicie. They have but one addominal 

 thread. 



The Thalassemae are divided into 



Thalassema, jsropc?', 

 AVhcre these two hooks are placed far forwards, and the posterior 

 extremity is destitute of seta^*; and 



ECHIURUS, 



Where the posterior extremity is furnished with transverse ranges 

 of setae. 



E. vulgaris; Lumbricus echiurus, Gm.; Pall., Misccl., Zool., 

 XI, 1 — 6. Found along the coast of France in siiidy bottoms. 

 It is used as bait by fishermen. 



Sternasi'Is, Otto, 

 Where, in addition to the setee of the Echiuri, we observe ante- 

 riorly a slightly corneous disk surrounded with cilia f. 



CLASS II. 



ENTOZOA, Bud. 



The Entozoa or Intestinal Worms are remarkable, because the 

 greater number inhabit the interior of other animals, and there only 

 can propagate. There is scarcely a single animal that is not the 

 domicil of several kinds, and those Avhich are observed in one species 

 are rarely found in many others. They not only inhabit the alimen- 

 tary canal and the ducts that empty into it, such as the hepatic 

 vessels, but even the cellular tissue, and the parenchyma of the most 

 completely invested /iscera, svich as the liver and brain. 



The difficulty of conceiving how they get there, added to the fact 

 of their never having been seen out of living bodies, has induced 

 some naturalists to believe that they are spontaneously engendered. 

 AVe now know that most of them not only evidently produce ova or 

 living young ones, but that in many, the sexes are separate, and 



* Thalassema Neptuni, Gert., or Lambricus thalassema, Pall. Spicil. Zool., fasc. X, 

 tab. I, fig. 6 ; — Thalassema mutatorium, Montag., Lin. Trans., XI, v, 26, may not 

 differ from the preceding one. 



t Thalassema scutatum, llanzan., Dec. I, pi. 1, f. 10 — 12, or Sternaspis thulus- 

 semoides, Otto, Monog. 



A lute examination of the Tlwlasscma: has proved to me that this is their proper 

 place. 



