F [ 381 j 
XL. On the Anatomy of Distoma clavatum, Rud. By Ricuarp Owen, Esq., F.R.S. & 
Z.8., Assistant Conservator of the Museum of the Royal College of Surgeons in London. 
Communicated May 26, 1835. 
IN former papers' I gave descriptions of two Entozoa, or internal animal parasites, of 
, widely different degrees of organization: the one manifesting simply a homogeneous 
granular pulp, enveloped in a transparent thin elastic tegument; the other having di- 
stinctly developed nervous ganglions and filaments, a muscular tunic, a digestive canal 
contained in an abdominal cavity, ovaries, oviduct, and fecundating glands. I now 
propose to offer a few observations on an Entozoon of an intermediate grade of struc- 
ture, in which a cellular parenchyma still occupies the body, where no distinct ner- 
vous filament can be traced, but in which a complicated system of nutritious and gene- 
rative canals, with external organs for adhesion and locomotion, are developed. 
My attention was first called to the species of Distoma about to be described by the 
following circumstance. In the series of the Hunterian collection of comparative ana- 
tomy relating to the digestive functions, there is a preparation? of an Acrite Invertebrate 
animal, of a round elongated form, showing at one extremity a sac opening externally 
by a minute orifice ; and at the opposite end a larger orifice surrounded by a suctorious 
disc, behind which, and at a little distance from each other, are two other orifices, the 
posterior being of large size, and evidently an organ of adhesion. From the manuscript 
catalogue it appeared that Mr. Hunter had regarded the sac as the stomach. 
I was for some time uncertain to what class of animals this singular specimen 
could belong, but was inclined to refer it to the Trematode, or fluke-worms, on account 
of the suctorious orifices at the smaller end; although the digestive cavity, which 
the specimen had apparently been prepared to exhibit, was a feature in its organiza- 
tion which appeared to remove it equally from that and any other order of the Ster- 
elmintha. Subsequently, however, on looking over the ‘Spicilegia Zoologica’ of 
Pallas, I found, in the tenth fasciculus, a figure and description of a Worm termed Fas- 
ciola ventricosa, which closely resembled the animal in question. The general form and 
situation of the different orifices were the same, but the orifice corresponding to that 
which led to the cavity regarded by Mr. Hunter as the stomach, Pallas calls the anus. 
The account given of the cellular parenchyma of the body, of its dark-coloured con- 
tents, and yellow ovula, agreed very closely with the appearances in the Hunterian speci- 
men, but nothing could be deduced from the description as to the existence of any cavity 
communicating with the anus, corresponding to that which the Hunterian specimen 
presented ; and the figures given by Pallas illustrate the external form only. The size 
of the specimen described in the ‘ Spicilegia’ is nearly 2 inches in length, and 3 of an 
1 Page 315 and page 325. ® No, 116. 
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