ENTOZOA. 403 
canal resembles that of the Bonelliz. They have but one addominal 
thread. ; 
The Thalasseme are divided into 
THALASSEMA, proper, 
Where these two hooks are placed far forwards, and the posterior 
extremity is destitute of setae*; and 
Ecuivurvus, 
Where the posterior extremity is furnished with transverse ranges 
of setae. 
E. vulgaris; Lumbricus echiurus, Gm.; Pall., Miscel., Zool., 
XI, 1—6. Found along the coast of France in sandy bottoms. 
It is used as bait by fishermen. 
STERNASPIS, Otto, 
Where, in addition to the sete of the Echiuri, we observe ante- 
riorly a slightly corneous disk surrounded with cilia f. 
CLASS II. 
ENTOZOA, Rud. 
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 which 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, such 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. 
We 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. 
+ Thalassema scutatum, Ranzan., Dec. I, pl. 1, f. 10—12, or Sternaspis thalas- 
semotdes, Otto, Monog. 
A late examination of the Thalasseme has proved to me that this is their proper 
place. 
