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PROCEEDINGS OF THE 



[April, 1857 



trace of their original independence ; for while the capsules are 

 symmetrically distributed when compared with each other in posi- 

 tion, they are nearly always asymmetrically placed with regard 

 to the tentacula in their neighborhood, each capsule being nearer 

 to one of the two tentacula between which it occurs than to the 

 other: and when, as in some instances, the capsule is actually 

 connected, with the base of a tentaculum, it is placed on one side 

 of it. Nor is this want of symmetrical position, visible in the re- 

 lation of the capsules to the tentacula only but it is frequently 

 equally so, in their relative position to the radiate tubes, whose 

 symmetrical relation is the same as that of the tentacula. In 

 short, it appears, that we shall be obliged, as our knowledge in- 

 creases, to look upon the membranous ring, which Forbes ele- 

 gantly styled a vail (velum) as not merely a prolongation and 

 folding in of the bell-wall but a very distinct structure, having its 

 own peculiar appendages, distributed according to its own pecu- 

 liar symmetrical law. In that case, from embryological data, we 

 should regard the capsules as appendages of the vail, while the 

 tentacula belong to the bell-wall, and though the bell-margin is 

 formed by the union of these two structures, and their several ap- 

 pendages are brought thus closely together yet even in this 

 union, the disagreement of their symmetrical laws is preserved, 

 introducing thus one of those beautiful instances of the expression 

 of special thought, by a departure from mathematical symmetry, 

 which are so frequently exhibited in the works of the great Mas- 

 ter-Artist, and to an imitation of which human art so rarely attains. 



There are, however, a few genera in which the position of the 

 capsules appears to be more nearly symmetrical with that of the 

 tentacula than usual. But so far as my acquaintance with the 

 subject goes, this occurs only where both kinds of appendages are 

 numerously represented in adult and fully grown specimens, so 

 that the original want of agreement in symmetry has been gradu- 

 ally disguised by the filling up of the unequal spaces through the 

 multiplication of organs of both kinds. These remarkable organs 

 may be described as each consisting of a transparent membranous 

 oval or spherical cyst, projecting from the bell-margin, and con- 

 nected with a ganglion-like enlargement of the marginal cord, 

 (See pi. 12, fig. 2, L). Within, each contains a variable num- 

 ber of round or polyedral corpuscles which have been considered 

 otoliths, and certainly appear in some instances to contain inor- 

 ganic deposit. Their function is still unknown. 



