CIRRATULUS. 211 



brown or yellowish colour, much stained from the internal viscera. 

 Head somewhat flattened, biannular, small, naked, marked on each 

 side with a curved black line, the two segments posterior to it without 

 filaments or feet. Segments numerous, rather narrow; from the 

 anterior margin of the fourth, which becomes suddenly larger, arises 

 on each side, but dorsad, a bundle of filaments shorter, generally 

 more tortuous and of a paler colour than the others, which arise 

 from the sides of the following rings down about one-fifth of the 

 length of the animal, and a few remote filaments are dispersed irre- 

 gularly on the rest of the body. There are two rows of slightly 

 protuberant small papillary feet on each side, with a considerable 

 interval between the rows ; each papilla armed with from three to 

 six bristles ; the bristles of the superior longer, slenderer, and more 

 acutely pointed than those of the inferior, which are few in number, 

 stout and curved near the apex : no spines. Anus terminal, forming 

 a plain aperture with a dorsad aspect (No. XXXVII.). 



C. borealis lurks under stones, in a somewhat muddy soil, in which 

 it forms burrows similar to those of the earth-worm, and into which 

 it retires slowly when disturbed. The filaments by which it is so 

 remarkably distinguished, and which curl around it like as many 

 parasitical worms, are the branchiae, or organs through the medium 

 of which the blood is exposed to the influence of the air, and fitted 

 for the purposes of life. They take their rise from above the dorsal 

 feet, some from the back itself, are about twenty in number on each 

 side, tortuous or extended, unequal in their lengths, the shortest 

 being placed anteriorly, but the gradation is not regular ; and they 

 are very easily removed by handling or by immersion in fresh water. 

 They consist of a large central vessel carrying red blood, surrounded 

 by a white gelatinous transparent membrane, and are consequently 

 of a fine red colour ; but this is liable to variation, for some, par- 

 ticularly the anterior bundles, are often quite white, and others, again, 

 are occasionally spotted, as from a partial stagnation of the blood in 

 them. When magnified they appear to be crenulated, but are not 

 fringed with cilia. Messrs. Audouin and Milne-Edwards propose to 

 restrict the term hranchicB to the paler kind which are inserted in 

 fascicles on the margin of one of the anterior segments, and they 

 call the scattered filaments cirri ; but surely, their function and 

 structure being acknowledged to be identical, a name expressive of 

 any difl*erence in either respect is liable to objection. They also 

 describe the feet as composed of two branches, but this is a mere 

 anatomical fiction, for there is really no common base and no bifur- 

 cation, the upper and lower papillae being separate, and divided by a 

 considerable interspace ; and on the posterior segments these papillse 

 are so slightly protuberant as to be scarce perceptible. The bristles 

 are of two kinds : from the superior papillae there issue about six, 

 three of them long and slender, and three shorter and comparatively 

 stout, — all of them simple, unjointed, and acute. The bristles of 

 the inferior papillae vary from three to one only in the caudal seg- 

 ments, and they are all stout and curved like the italic letter y*. 



Obs. I willingly follow Oersted in the synonymy of this species, 



p2 



