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XLII. Remarks on the Entozoa, and on the structural Differences existing among them: in- 
cluding Suggestions for their Distribution into other Classes. 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 investigating the nature of the small human Entozoon which I have called Tri- 
china, considerable difficulty, extrinsic, or superadded to the subject itself, was expe- 
rienced, from the habit of considering all such internal parasites as belonging to, or 
constituting, a distinct class of animals. It is true that it was easy to determine in Tri- 
china the absence of trachee, of branchie, and of every other kind of respiratory organs, 
as well as of any true circulating organs, and that not even a vestige of a nervous chord 
existed in this worm-like animal. But its reference to the Entozoa was not therefore less 
a matter of doubt ; for other negative characters presented themselves in relation to the 
digestive system, and to the mechanism for adhesion or suction, which no less prevented 
its association with already known Entozoa, than the first-mentioned deficiencies sepa- 
rated it, in common with the Entozoa, from Worms of a higher type of organization. 
The greater part of Cuvier’s definition of the class Entozoa is devoted to the account 
of their localities, and the remedies used against them, and to a consideration of their 
mode of production ; while the character itself of the class is altogether a negative one. 
**On n’apercoit aux vers intestinaux ni trachées, ni branchies, ni aucun autre organe 
de la respiration, et ils doivent éprouver les influences de l’oxygéne par l’intermédiaire 
des animaux qu’ils habitent. Ils n’offrent aucune trace d’une vraie circulation, et l’on 
n’y voit que des vestiges de nerfs assez obscurs, pour que plusieurs naturalistes en aient 
mis l’existence en doute.”” Cuvier then adds: ‘‘ Lorsque ces caractéres se trouvent ré- 
unis dans un animal, avec une forme semblable a celle de cette classe, nous l’y rangeons, 
quoiqu’il n’habite pas dans l’intérieur d’une autre espéce!.” 
In consistency with this proposition, the Vibriones of Miller ought to have ranked in 
the ‘ Régne Animal’ with the Entozoa; and it would be difficult to determine what mo- 
dification of external form should exclude a species defective in respiratory or circu- 
lating organs from that class which, even in Cuvier’s system, includes animals of 
almost every variety of shape. Fortunately, however, the presence of external vibra- 
tile cilia, which are in some degree subservient to respiration, affords a good character 
for distinguishing the simpler Infusoria from the Entozoa, although with this limitation 
those species of non-ciliated Vibriones?, which do not occasion currents when placed in 
a coloured fluid, would still rank with the Intestinal Worms. 
' Régne Anim., nouy. ed., tom. iil. p. 246. 
2 Amblyura Serpentulus, Ehr.; Anguillula Aceti, Auct.; and Ang. Glutinis, Auct. or the common Vinegar-eel 
and Paste-eel. 
