86 OBIGIZfAL ABTICLES.
base. In the fira^^ments removed very cautiously with a knife, I could recognise what appeared to be portions of simple tentacula, muscular fibres and a fibrous matrix, brown pigment cells, the usual yellow or amber-tinted spherical globules of the subjacent parts, and ciliated epithelium, from the lining of the common cavity. The analogy of other cases suggests the probability that the tentacula correspond with the outer whorl of loculi.
The most remarkable circumstance connected with these polyps, is the invariable presence of a little solitary Sipwnculua in a beauti- fully excavated burrow at the base of the eorallum. The uniform position of the opening and sinistral direction of this burrow, first observed in dead specimens, led me to suppose that it was in some way coimected with the economy of the polyps themselves, but having discovered its occupant to be one of the coral perforating Sipun- culida, which abound in the South Seas, the nddle was quickly solved. The body of one of these parasites, taken from a Bellona Beef specimen, is about i of an inch in length, terete, but |;raduaUy increasing in diameter from before backwards, and exhibiting a permanent curvature forwards, corresponding with that of the bur- row.
The crested proboscis is about three times the length of the body, and crowned with simple ciliated tentacula. On the dorsal surface, immediately behind the base of the proboscis, is a little oval and brownish callosity, answering the purpose of an operculum, when the animal is retracted into ito cell, and close behind this disk is the anal aperture. The posterior extremity of the body is furnished with a similarly constituted, but slightly conical, shield. As the opercular disk meets the rest of the dorsal surface, at an angle more or less obtuse, the proboscis appears to hold a subterminal ventral position, and protrudes itself somewhat perpendicularly to the axis of the body. The surface of the latter is beset with minute asperities, dis* posed serially, or irregularly scattered. These become larger and more numerous towards the dorsal region, and more de&iitely aggre- gated at the extremities ; they constitute the before mentioned oper- cular and caudal disks. As they extend themselves on the proboscis they grow smaller, and begin to assume a more orderly arran£;ement, and mially form into closely set rings of minute and recurved hooks, reaching to the base of the oral tentacula. This parasite is evidently closely allied to the little animal from the Indian seas, named LUho' dermis ctmeu9^ by Guvier, and which was the only species known to him.
In the Coral borers, which are nearly identical with the little animals here noticed, I found that the OBsophagus was encircled by a nervous collar, with a cephalic enlargement on either side, from which tentacular nerves arose, and, in contact with which, dark eye specks were distinctly visible ; there is also a single ventral nervous diord, giving off lateral nerves at stated intervals, but without any very appa- . rent ganglionic dilatations. I observed, moreover, that the cavity of
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