PROF. OWEN ON A NEW SPECIES OF EUPLECTELLA. 119 
up chiefly of portions of a coarse irregular siliceous sponge, which appears to be foreign to 
the proper body of the Buplectella, and includes some shells and other marine calcareous 
bodies. Some of the fine long fibrils, emerging from the mass, converge, as they are reflected 
back (fig. 2), and, after a few graceful bendings, again diverge into separate wavy locks of 
the most delicate hairs, having a silken or silvery lustre (h, h, figs. 1 & 2). The whole of 
this beautiful elongated filamentous medium of attachment of the Euplectella may be 
compared to a lock or tuft of the hair which Poets feign to have adorned the head of 
the Syren or Mermaid. 
The number of the longitudinal fibres at the base of the cone in Euplectella Asper- 
gillum is sixty, in Euplectella Cucumer it is fifty-three: their number at the apex in 
Euplectella Aspergillum is thirty, in Euplectella Cucumer it is thirty-five. I would not, 
however, be understood as confiding in these particular numbers being constant and cha- 
racteristic of the species. The fibres of the reticulate cap consist of converging and of 
connecting or transverse kinds : many of the former are continued from the confluence 
of two of the longitudinal fibres of the cylindroid, where they become bent at nearly right 
angles after leaving the connecting marginal band to form the cap: such fibres show a 
thickness proportionate to the additional material entering into their composition. The 
degree of irregularity in the converging and connecting fibres forming the reticulate cap 
is like that in Euplectella Aspergillum*. The superficial fine oblique series of fibres, with 
the superadded multiradiate spicula, terminate abruptly at the marginal rim in Euplee- 
tella Cucumer, just as the ridges of the cylinder terminate in Fuplectella Aspergillum. 
Dr. A. Farre notes, as the result of his study of the structure of the Huplectella Cucumer, 
that *the oblique lines are not formed out of one continuous line of fibre for each side, 
wound round and round, which is the idea of a spiral, but they consist of a double series of 
ellipses, placed at definite distances, which intersect each other at right angles, or nearly so. 
These form perfect ellipses only towards the centre of the specimen, for at either end they 
are necessarily interrupted. In these oblique fibres there occur the same confluence of two 
contiguous lines, in some places, and divergence or bifurcation of simple ones in others, 
as happen in the longitudinal series, and evidently with the same object of adapting their 
arrangement to the increasing or diminishing diameter of the cylinder. With regard to 
the relative positions of the longitudinal, transverse and oblique fibres, I find that these 
lie in several alternate series. First a bundle of about half-a-dozen longitudinal close- 
lying fibres. These run straight from end to end of the cylinder, " : 
' except where they bifurcate or combine. Then the looser bundles of oblique fibres 
decussate with the longitudinal ones, the fibres separating to pass over, under, and 
between them, and at the same time intersecting the fibres of the opposite oblique series 
in a similar way, 
* Compare PI. 13, Trans. Zool. Soc. vol. iii. fig. 2, with fig. 2 in PI. XXI. 
