532 Prof. M'lntosh's Notes from the 



three or four times as long as the adjoining, and ends in a 

 hook with a secondary process in the form of a fixed process 

 beneath — that is, in the concavity. Whilst only three of these 

 organs project externally, seven occur in an even row in tiie 

 tissues, but four are imperfectly developed. Of the three 

 projecting externally, two are larger and more opaque 

 (brownish), have short segments throughout their lower half, 

 longer segments in their distal half, which is curved. The 

 third bristle is considerably shorter, more translucent, and has 

 long segments throughout its free portion, with short segments 

 at its base in the tissues. The latter apparently represents 

 a developing bristle. The dorsal bristles project upward and 

 inward in a series of short fans to the posterior end of the 

 body, the tips showing a tendency to curve forward. The 

 ventral bristles from the third backward present a gradual 

 modification into stout hooks with bitid tips. Thus at the 

 10th foot these processes retain a bristle-like appearance 

 with long articulations, which, however, become shorter 

 toward the tip, which tapers to a long terminal joint with a 

 hook and a secondary process differentiated at its free edge, 

 viz., with a thickened rim, but the whole is bound to the 

 concavity of the hook. At the 20fch foot a similar condition 

 exists both as regards the bristle-like stem of the appendage, 

 the shorteniug of the joints toward the tip, and the longer 

 terminal joint with the hook and the fixed secondary process 

 beneath with the marginal differentiation — the whole having 

 the aspect of a Polyzoan avicularian. The hook gradually 

 becomes shorter, broader, and stouter, the articulations more 

 closely arranged, and between the 40th and 50th feet the 

 secondary process has in some lost its web, so that the 

 thickened edge, as it were, forms the mandible below the 

 hooked beak. Toward the tip of the tail the secondary pro- 

 cess of the now short hook often disappears and the terminal 

 hook is considerably abraded. The hook is still flattened and 

 has oblique striae below the translucent tip. The reticulations 

 are also very closely arranged. 



Flahelligera affinis, Sars, is a common form all round the 

 shores of Britain from Shetland to the Channel Islands, and 

 is equally well known in iSpitzbergen, Greenland, Iceland, 

 and Scandinavia. It generally occurs between tide-marks or 

 in the Laminarian region, though it also extends to the 

 coralline zone. So far as observed, all the British examples 

 are referable to the same species. 



