238 MR. J. D. MACDONALD ON THE ANATOMY AND 



coincidence or casualty. It would rather seem to indicate the fulfilment of some im- 

 portant end in the propagation of the species. Mr. F. M. Rayner suggested to me that 

 the phenomena of reproduction in the case of Tcenia and Bothriocephalus afford a curious 

 parallel to the circumstance just alluded to with reference to the Mbalolo. The trans- 

 verse fission in the latter case is evidently connected with the dispersion of the ova, rather 

 than the development of new individuals from the pre-existing materials of the animal's 

 body, as in Nereis, &c. 



I had the good fortune to discover a single head of the Mbalolo, — and the only one to 

 be found amongst a large bottleful of bodies and tails collected for me by my esteemed 

 friend, the Rev. S. Waterhouse, Wesleyan Missionary, Fiji. The joints of the body, to the 

 number of about twenty, remaining in connexion with the head, were considerably smaller 

 than those that would succeed them were the specimen perfect ; besides which, the aciculi, 

 of two sorts, were more numerous in the little bundles springing from the lateral tuber- 

 cles. The dark spots and characteristic marldngs of the dorsal surface were also very 

 faint, or scarcely distinguishable. The head itself was very little narrower than the joints 

 of the neck, blunt and rounded, with a slight emargination in front. Eyes two, placed one 

 on either side of the upper surface, including, in the space between them, three conical 

 tentacula, of which the central is the longest, and projects a little beyond the head. 

 The mouth was inferior, subterminal, and armed with two pairs of jaws — those of the first 

 pair being sickle-shaped and simple, and those of the second broad and jaw-like, having 

 a curved external outline and a series of dental points on their opposable border. The 

 tissues in the neighbourhood of the jaws appear to be much indurated ; and one structure 

 in particular is worthy of notice, that its true nature, if not already known, may be inves- 

 tigated in the neighbouring genera. It consists of two slightly diverging series of scale- 

 like plates overlapping one another from before backwards, in which dii'ectiou also they 

 gradually increase in size. The free edges of the plates are directed backwards ; and as 

 distinct muscular bundles may be traced into their deep surface, it is highly probable 

 that they are capable of elevation and depression, acting, so to speak, as a prehensile 

 palate, opposable to the jaws. 



The typical elements of the lateral appendages of the body-segments (often so distinctly 

 seen in allied Annelida) appear to have become blended together, more or less, so as to form 

 a single setigerous tubercle, transmitting, however, as is usual, two characteristic kinds 

 of setae, and bearing a simple papilla-like, dorsal cu-rus above, and a somewhat smaller 

 ventral cii'rus below, — the former lying near the outer extremity of the tubercle, and the 

 latter somewhat nearer the base. The repetition of these cirri may be traced backwards, 

 through aU the annuli, to the penultimate joint, in which they are quite suppressed ; but 

 both reappear in the anal segment, and the ventral cirri in particular, having attained 

 considerable length, project posteriorly like those of better-known Nereids. Besides the 

 supporting stylets of the feet (exhibiting so much sameness of character in all the Anne- 

 lida furnished with them), the setse of Mbalolo, as above noticed, are of two distinct 

 kinds — one being of a very long slender and bristle-like form slightly compressed on the 

 sides, twisted on its long axis, and terminating in an exquisitely fine point; while the other 

 is much stouter and shorter, with a small claw-like terminal appendage having two 



