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OKIGrN'AL AETICLES. 



"base. In tlie fragments removed very cautiously with a knife, I 

 could recognise what appeared to be portions of simple tentacula, 

 muscular fibres and a fibrous matrix, bro-\\m 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 coimected with these polyps, 

 is the invariable presence of a little solitary Sipimculus in a beauti- 

 fully excavated burrow at the base of the corallum. The imilbrm 

 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 connected with the economy of the polyps themselves, but having 

 discovered its occupant to be one of the coral perforating Sipun- 

 culidcs, which abound in the South Seas, the riddle was quickly 

 solved. Tlie body of one of these parasites, taken from a Bellona 

 Eeef specimen, is about f of an inch in length, terete, but gradually 

 increasing in diameter from before backwards, and exhibiting a 

 permanent curvature forwards, corresponding Avith that of the bur- 

 row. 



The crested proboscis is about three times the length of the body, 

 and crowned Avith 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 its 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 witli minute asperities, dis- 

 posed serially, or irregidarly scattered. These become larger and 

 more numerous towards the dorsal region, and more definitely ago-re- 

 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 arrangement, 

 and finally 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 LifJio- 

 dermis ciineus, by Cuvier, and which was the only species knoAAoi to 

 him. 



_ In the Coral borers, Avhich are nearly identical with the little 

 annuals here noticed, I found that the oesophagus 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 distmctly visible ; there is also a single ventral nervous chord, 

 givmg off lateral ner\es at stated intervals, but without any very appa- 

 rent ganglionic dilatations. I observed, moreover, that the cavity of 



