184 TEREBELLA. 
The littoral Terebella, expelled from its tube, is of a vermicular form ; 
the body seven or eight inches long, and a quarter of an inch thick towards 
the head, and consists of numerous segments tapering towards the posterior 
extremity, which terminates in several points.—Plate XXVI. fig. 1. Six- 
teen retractile pencils, each of fifteen or twenty bristles, border the sides 
of the upper segments, which farther down degenerate to stumps. The an- 
terior part of the body consists of a thin frill, divided into three portions, 
surrounding the roots of sixty, seventy, or a hundred tentacula, according 
to the age or dimensions of the specimen, with the mouth like a scoop 
in the midst of them. Immediately behind this frill, three pair of the 
most beautiful scarlet branchize rise half an inch high. The animal is 
universally of peach-blossom colour, variable in a redder or browner tinge, 
with a broad, taper, smooth, velvet, bright carmine stripe, descending 
along the belly between a transverse row of ellipses.—Plate XXVI. fig. 1, 
Terebella, reduced ; fig. 2, section of the body. 
An easier guide than following the preceding description, consists 
in simply observing the formation of the branchiz, to identify the 
different species of the Terebella. These organs are extremely diversi- 
fied, sometimes in number, always in structure. It is somewhat singu- 
lar to remark, that naturalists give one set of branchiz as that of the 
Terebella conchilega, though actually not belonging to the species, for 
an. illustration of all the rest. But we must allow that the observer's 
most attentive inspection is indispensable. This organ becomes a micro- 
scopical object, about which no one can readily satisfy himself; its 
expansion and contraction are incessant, thence nothing is of more diffi- 
cult delineation. 
The branchis: of every species of Terebella, I say, are different. 
Here they are so complex and luxuriant, they abound in such numerous 
points, extremities, and curvature ; their shades and intensity of colour, 
and the alternation of shape are so variable, that no object is more 
beautiful and interesting to behold, or more difficult to be rendered in- 
telligible by description. To attempt it would be vain. The mind alone 
must conceive it. During life, the motion, the enlargement, reduction, 
and spiral twisting of the branchix, singly or collectively, is perpetual, 
