i i i i i i ee 

MR. R. OWEN ON THE ANATOMY OF LINGUATULA TANIOIDES. 329 
that in the Slug (Limaz), in which the nerves of the body radiate nearly in a sym- 
metrical manner from a single subcesophageal ganglion, the two posterior filaments 
being the longest, and extending almost parallel to each other to the posterior extre- 
mity of the body. It may also be observed, that the disposition of the muscular system 
in Limaz is analogous to that of Linguatula, being most developed at the sides of the 
foot, and least along the middle line, which is thin and Semitransparent when viewed 
against the light. If one might be permitted to trace further the analogy of form sub- 
sisting between genera so widely separated in other important particulars, the two 
foss@, with their little hooks, on either side of the mouth of Linguatula, might be com- 
pared with the two depressions which, when the tentacles are retracted, appear in the 
_ Same situation in the head of the Slug. It is the superior organization of these parts 
which renders necessary the further development of the nervous system of the Slug ; 
and the completion of the cerebral ring and the development of the supracesophageal 
ganglion constitute the chief difference subsisting between it and Linguatula in this part 
of their organization, 
The superior powers of locomotion with which the Slug is endowed render it necessary 
that it should have organs of sense sufficiently developed to explore and take cognisance 
of the various circumstances in which it may be placed. The action of the muscles 
occasions waste, and demands a proportionate supply of new material for its continu- 
ance: hence the necessity of the superaddition of a vascular system for the carriage of 
the restorative molecules, of a more complex digestive apparatus for their supply, and 
of respiratory and secretory organs for the elimination of the waste parts of the 
body. 
In Linguatula, on the contrary, the sphere of action being limited to a dark cavity 
in the interior of another animal’s body, the necessity for these superadded structures 
does not exist. Its food, being already animalized, requires only a simple canal to com- 
plete its assimilation, without the assistance of teeth or salivary or biliary organs. 
Neither heart nor vessels are perceptible, and it is probable that nutrition is effected 
by transudation and imbibition ; and here we may notice the admirable arrangement of 
the oviduct with reference to the reception of the materials for the full development of 
the myriads of ova which it contains. 
Living in a cavity to which external air has access, it might be expected that the 
vital phenomena of Linguatula would be more energetic than in other Entozoa. With 
respect to its muscular actions, Rudolphi observes: ‘‘ Motus peculiares, vermium tere- 
tium tamen agitationibus maxime accedunt, partem nimirum tam anticam quam posti- 
cam continuo vel reflectit vel inflectit, minore tamen, quam illi, corporis vi utitur, 
neque cutis musculorum apparatum notabilem continet. A Trematodum, vel Distoma- 
tum, vel Amphistomatum et Monostomatum, vel etiam Polystomatis uncinulati, moti- 
bus quam maxime recedit, neque cum Tzniis ullo modo comparari potest '.” 
’ Hist. Ent., tom. ii. p. 443. 
