SABELLARIA SPINULOSA. 19 



anterior tuft is the largest and the third the smallest, the opposite condition occurring in 

 the large dorsal bristles. The direction of these bristles is forward and slightly inward, 

 the angle of inclination being thus different from that in the next series. The last 

 (third) set shows faint serrations or striae at the sides just below the flat tip. 



Between the ventral edge of the lamella for the hooks and the ventral bristles in the 

 second (abdominal) region of the body is a small filiform papilla, longest in front and 

 diminishing to a minute process in the caudal region. 



The succeeding region of the body is characterised by the increase in the depth 

 of the lateral lamellae, the first being about three times that of the next in front 

 (Plate CXII, fig. 1) ; but they gradually diminish in depth in their progress backward, 

 whilst they increase in prominence, those in the distal part of the region, for no dorsal 

 bristles are visible, projecting like cirri. The bristles of the region are thus pushed 

 ventrally, so that even the long posterior forms are not, as a rule, seen at the sides in a 

 dorso- ventral view. They are situated to the inner side of the prominent, coloured 

 lamellae forming the dorsal region of each segment. The longest bristles in each tuft 

 are in front, since, instead of being arranged in a transverse row, they form an oblique 

 one. The typical bristles (Plate CXXIII, figs. 2/ and 2 g) are long and translucent 

 with smooth shafts, which taper from the skin to the delicate and flexible tip covered 

 with whorls of spikes directed distally. Their usual direction is forward and inward, 

 and they fall smoothly under a needle carried from behind forward, but rise against it 

 when passed in the opposite direction. As rudimentary bristles of the same kind appear 

 in the first region of the body between the bases of the spatulate forms, their distri- 

 bution is thus uniform throughout. Moreover, the bristles of the first series of this 

 region present a transition stage, having stouter shafts and a broader and shorter spinous 

 part at the tip, the latter, indeed, resembling a short villous region. Accompanying 

 these is usually a slender tapering spinous bristle, and this is also a transition form. 

 The posterior bristles form a conspicuous series ventally, but though longer their 

 structure remains the same. 



The prominent transverse or lateral lamellae formerly alluded to bear the numerous 

 hooks, their tendons and muscles. In shape the hooks (Plate CXXIII, fig. 2 h) are 

 elongate, with a single tendon at the distal end and two at the rounded base. In lateral 

 view five teeth usually characterise them, though when viewed from the front each 

 represents only one of two or three in the row, of which six may occur in both anterior 

 and posterior feet, the latter, however, having smaller hooks. The slender cirriform 

 lamellae of the posterior feet have the interior largely occupied by the bundles of tendons 

 from the hooks, and to these muscular fibres are attached. At the base of each elongated 

 lamella posteriorly is a deep brownish pigment-spot. 



The narrow posterior end of the body is continued as a long tubular process 

 (Plate CXII, fig. 1), which fits into the dorsal groove when the animal is quiescent in 

 the tube, but which can be elongated or shortened at will, and forms a very efficient 

 means for passing the faecal matter out of the aperture of the tube without necessitating 

 the turning of the annelid. At its tip is the vent with a more or less distinct rim, which 

 in some is oblique. It is noteworthy that in the preparations this tube is generally 

 dorsal, whereas that of S. alveolata is doubled forward in the ventral groove. The 



