318 MR. R. OWEN’S DESCRIPTION OF A MICROSCOPIC ENTOZOON 
genus in his ‘ Systema Entozoorum’, but refers the three species described by Zeder to 
the genera Filaria and Ascaris. The Capsularia Halecis, or Filaria Capsularia of Ru- 
dolphi, infests the abdominal viscera of the Herring, and measures from half an inch to 
an inch in length: the intestinal canal is distinct, and is dilated at one extremity into 
a stomach. In the males the intromittent spiculum protrudes from the anal extremity, 
which is the largest. The Capsularia Salaris and Capsularia trinodosa of Zeder repre- 
sent, according to Rudolphi, a single species of Ascaris (Asc. Capsularia, Rud.). They 
are about an inch in length, and are inclosed in a spiral form in cysts attached to the 
cellular surface of the peritoneum of the Salmon. The Capsularia Halecis figured by . 
Zeder! exhibits a straight alimentary canal and longitudinal lines, probably nervous fila- 
ments, which resemble those lines observable under certain circumstances in the present 
microscopic species, but no further correspondence in internal structure can be traced 
between them. 
The circumstance of being inclosed in cysts is common to many very differently 
organized genera of Entozoa. There are few indeed, with the exception of those which 
live upon the mucous surfaces of the body, that do not, by exciting the adhesive in- 
flammation, become inclosed within an adventitious cyst of condensed cellular sub- 
stance analogous to the galls produced by the irritation of Jarve developed in the sub- 
stance of a living vegetable. 
The simple type of structure, which the minute animal here described exhibits, ap- 
proximates it to the lower organized groups of the Vers Intestinaux Parenchymateux of 
Cuvier ; and both from its locality and the constancy of the cyst inclosing it, it mani- 
fests a relation of analogy to the order Cystica of Rudolphi. From all the genera of 
this order, however, it differs in the want of the complex armature of the head and of 
the dilated vesicle of the tail. At first sight it might seem indicative of an annectant 
group, which would complete the circular arrangement of the Entozoa, by combining the 
form of the Filarie of the first, with some of the characteristics of the Cysticerci of the 
last, of Rudolphi’s orders. Unfortunately, however, the class Entozoa as it now stands 
is so constituted that an animal may be referred to it without much real or available 
knowledge of its organization being thereby afforded: it embraces animals with the 
molecular and animals with the filiform conditions of the nervous system ; conditions 
which are accompanied by different types of the digestive system, and which indicate 
not merely differences of class, but of primary division in the animal kingdom. 
The organic form in the natural system, to which I consider the animal under con- 
sideration as being most nearly allied, is that exhibited by the lower organized Vibriones 
of Miller, and of which Ehrenberg has composed his genera Vibrio, Spirillum, and 
Bacterium: so that the present species may be regarded as affording, with the seminal 
Cercari@, a second example from the lowest class of the animal kingdom having its 
1 Naturgeschichte der Eingeweidewiirmer, tab. i. figg. 3, 4, 5. 

