MUSCULAR SYSTEM. 25 



(2.) Rotatory Muscles of the Crown. 



These also consist of two fasciculi (PL IV, fig. 4; V, fig. 5 ; IX, fig. 7, p), which arise 

 along with the set just described, and passing forward in company with these, separate from 

 them at some distance below the crown, and thence pass outwards to the right and left, to 

 be inserted each into its own side of the lophophore. Action : they rotate the tentacular 

 crown, and depress the lobes. 



(3.) Tentacular Muscles ? 



Under this name may perhaps be described a set of delicate parallel bands (PI. V, 

 fig. 5, q). to which attention was first directed by Van Beneden, and which may be observed 

 running from below upwards upon the margin of the lophophore ; these bands are continuous 

 with one another below, and when they arrive at the intervals between the roots of the 

 tentacula, each divides into two others, which would appear to run along the opposed sides 

 of two neighbouring tentacula. M. Van Beneden considers them as muscles destined to act 

 on the tentacula ; but it must be admitted that we are scarcely justified in pronouncing 

 decidedly on the muscular nature of these bands, which certainly do not present any distinctly 

 fibrous structure. If they be truly muscular, it is to their action that the various motions 

 observed in the tentacles would seem to be chiefly due. The margin of the lophophore 

 in the interval of the bands presents an oval transparent space, which looks exactly like an 

 aperture, and it would seem to be these spaces which M. Van Beneden has taken for " aqui- 

 ferous mouths;" after very careful examination, however, I have convinced myself that no 

 aperture exists here, the apparent mouths being merely transparent spaces in the 

 lophophore.* 



(4.) Elevator Muscle of the Epistome. 



This is a small but very evident fasciculus (PI. II, fig. 24, r), occupying the interior of 

 the epistome, and visible through its transparent walls ; it arises from the lophophore within 

 the cavity of the epistome, and then passing obliquely across the cavity, is inserted into 

 the inner surface of the oral wall of the epistome. Action -. it elevates the epistome, and 

 draws it away from the mouth. 



* M. Van Beneden has himself given up his earlier views upon this point, and has referred the 

 appearance in question to its proper cause. Dumortier and Van Beneden, Hist. Nat. des Polypes 

 composes d'eau douce, 2de partie, ' Mem. de I'Acad. R03'. des Sc. et Belles-lettres de Bruxelies,' 

 Compl., t. xvi. 



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