SABELLA PENIOILLTJS. 22T 



furrow, the firm and thick edge of the rim which carries the branchiae being severed and 

 neatly curved on each side ; the rim then passing ventrally to the base of the great flaps- 

 is folded inward and upward, and is fused on each side with the firm median mass over 

 the mouth. In the perfect condition with the branchiae attached the pedicle between the 

 ventral flaps passes upward as a bifid process, then expands on each side into a lateral 

 flap or wing, which after a short progress bends backward and upward, makes a kind 

 of frilled knee, and becomes continuous with the investing membrane of the branchiae of 

 its side, its outer border inferiorly passing into the basal semicircle of the branchiae, to 

 which it is fixed throughout. Such is the arrangement connected with the floor of the 

 mouth and the lower lip. Dorsally the membrane forming the roof of the mouth splits 

 considerably in front of the median fissure of the lower lip into two limbs, each of which 

 at the base has an axis with a narrow ventral web, and a thinner and broader dorsal web 

 which tapers distally and goes much further along the axis than the former, the axis 

 finally tapering to a long, delicate tip. The whole forms the so-called tentacle, which in 

 the preparations is concealed in each branchial semicircle. Viewed from the inner 

 surface of each branchial fan the " tentacle " has the web on its dorsal edge connected 

 with the dorsal edge of the fan, whilst its ventral web passes ventrally to the central 

 region dorsad of the mouth. The inrush of water along the inner surface of the branchial 

 fan would thus be swept toward the mouth, the tentacles and their webs probably aiding 

 in this function, and keeping the stream in each fan to its own side as it rushes down the 

 groove by the outer border of the smaller anterior web into the mouth. 



The branchial fan arises on each side from the firm base formerly mentioned, a spiral 

 twist being evident dorsally and more especially ventrally at its commencement. Each, 

 in preservation, has the ventral edge curved inward, and a narrow membranous web 

 passes from the frill of the inferior oral membrane for some distance along its edge. 

 This ventral border is the thickest and gives origin to the majority of the branchial 

 stems, the rest springing from the middle and posterior parts of the basal semicircle. 

 The number of these filaments varies, the two sides seldom being equal; thus, for 

 instance, thirty-eight may occur on the right and forty-one on the left. The fan on each 

 side is long and graceful, banded with regular markings of dull red and white. The 

 circles of colour do not go evenly round the expanded fan, but start from the ventral 

 fissure. Dorsally a greenish hue occurs in some at the base of the fan. In others green 

 or purple predominate, and the fluid in which the animals lie is always tinged with green 

 (Dalyell). 



Each filament has an elastic chordoid and camerated axis, the cameras being after 

 the fashion of the bristles of Nereis or Aricia. The filaments are united by a web inferiorly 

 (about the level of the first pigment-band), but free throughout the rest of their extent, 

 and are somewhat flattened processes with a smooth external edge, near which the axis 

 lies, whilst the inner edge is fringed with a dense series of slender pinnae, which likewise 

 have a translucent axis jointed at intervals like the bristles of the Chloroemidae. The 

 filaments and their translucent axis gradually diminish distally, but the axis can be traced 

 almost to the extremity. Toward the tip of the filament the pinnae gradually diminish 

 in length, finally forming mere papillae, and thereafter the tapering tip is smooth and of 

 moderate length. When the branchiae have lost their distal ends and regeneration has 



