ALCIOPIDJE. 113 



muscular fibres, the ends of which occur on each side of the first segment- junction. A 

 thin membranous flap dotted with cells and nuclei occurs in the front of each eye, and a 

 projecting narrower process of the same tissue apparently below it, whilst a subulate 

 tentacle, also thickly studded with deeply-stained nucleated cells passes forward a little 

 below the frontal edge. All the structures just described are delicate, and are 

 probably diaphanous during life. Moreover, they differ wholly from the appendages of 

 the male and female buds of Autolytus, and do not approach those of the Alciopidse. 

 A funnel-shaped depression with a median notch ventrally appears to indicate the oral 

 region, which thus is wide, and this segment, which is not clearly differentiated from 

 the head, bears on each side a foot directed obliquely forward and outward, and supported 

 by a strong translucent spine and a series of translucent bristles. The direction of these 

 feet shows that they have special functions — probably both protective and tactile. The 

 bristles are comparatively stout, and have a distinct curvature of the shaft below the 

 terminal dilatation, which is marked by a few oblique central strise. The distal end 

 is bevelled, and the terminal piece is of moderate length and simply hooked. These 

 bristles are borne by an elongated setigerous region slightly tapered from base to apex. 

 The dorsal cirrus somewhat resembles that of a Syllis, being long, slightly tapered and 

 articulated, and the same deeply-stained minute nuclei occur in these as in the cephalic 

 processes, but they are proportionally more numerous. They arise from the base of 

 the foot, and seem to have a short ceratophore, though the state of the preparation 

 rendered this indistinct. A short, simple, subulate ventral cirrus, again, is attached 

 inferiorly a little exterior to the base of the foot. The first foot is somewhat spindle- 

 shaped, and the rest present an ovate or elliptical dorsal process, apparently with a 

 special spine, but as only dorso-ventral views are obtainable further investigation is 

 necessary. Every foot, from the second to the last, is furnished with a very long, 

 translucent tuft of swimming-bristles. 



The body has fifteeen segments — diminishing gradually from the head backward, 

 the segment-junctions being boldly marked. The pygidium is slightly bipapillose, and 

 has two long caudal cirri which are longer and larger than the cirri immediately in front. 

 A pale moniliform streak passes from the mouth backward in the central line, and 

 probably represents the alimentary canal. 



The foregoing has the general outline of the Syllidae, and the appendages of the head 

 resemble those of the male of Autolytus (Polybostrichus), and also of Krohn's Syllis 

 prolifera, 1 the jointed cirri and the structure of the bristles especially recalling the latter. 

 The great size of the spines, and the presence of a considerable dorsal spine, however, 

 show divergence, and the minute structure of the head and mouth likewise differs. The 

 whole aspect, however, suggests relationship with a budding form, and in the present 

 uncertainty it is perhaps well to leave it in a separate position. 



The precise position of this form must, for the present, remain in abeyance until 

 more material is obtainable, but it conforms to no British type hitherto observed. 



1 ' Archiv. f. Naturges./ Bd. xviii, p. 66, Taf. iii, fig. 1 (1852). 



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