150 NERINE CIRRATULUS. 



In life the general aspect is greenish, the colour being deepest in front, with the 

 exception of the snout, tentacles, and buccal region, the former being pinkish, the latter 

 pale. The fine red branchiae, the blood in the dorsal vessel and in the tentacular vessels 

 enliven the outline, though only a single vascular loop is present in each branchia. The 

 tints vary in different specimens, as shown in some segments of a reddish form from St. 

 Andrews (Plate XCI, fig. 4). Mesnil found fragments of Ulva and diatoms, particularly 

 Schizonema, in the digestive tube. 



The first foot, like that of N. foliosa, is devoid of a branchia, though the upper lobe 

 from its development superiorly is somewhat lanceolate. It has a group of short, tapering 

 simple bristles with indications of a wing on each side of the tip. The ventral lobe is 

 proportionally more prominent than in iV. foliosa and forms a rounded lamella with a fan- 

 shaped group of short, tapering bristles. 



The second foot shows a well-marked branchia amalgamated with the inner base of 

 the upper lamella, which is now considerably elongated. A deep notch separates the two 

 distally, the blunt tip of the lamella contrasting with the acutely lanceolate tip of the 

 branchia. This division has a longer tuft of the finely tapered bristles, but from the 

 structure of the lamella they project less than those of the inferior division. The afferent 

 and efferent vessels form a loop considerably within the tip of the branchia. The ventral 

 division has a nearly semicircular lobe and a fan-like tuft of the finely tapered bristles 

 which project considerably beyond it. Indications of wings are visible in many of these 

 bristles. This and the previous foot thus differ from those of Ferine foliosa. 



The branchiae continue from the second foot backward to the posterior end, forming 

 in front narrow and acuminate processes, with frilled outer edges which curve over the 

 dorsum, then, proceeding backward, the external frill or border gradually decreases and 

 separates so as to form a free flap including only the base of the branchia. 



The tenth foot (Plate XCVII, fig. 2) presents dorsally the long, almost filiform 

 branchia, the coil of the included vessel leaving about one-sixth of the length at the tip 

 free. Nearly a third of its outer border is occupied by the upper flap of the division and 

 the free papilla at the tip projects upward in addition. The strong yet finely tapered 

 longer bristles extend obliquely upward considerably beyond the edge of the flap and only 

 traces of wings are present (Plate CV, figs. 1—1 1). The tips of the shorter bristles form 

 a regular series nearer the edge of the flap, and the broader and less tapered tips of these 

 show indications of wings. All are minutely dotted, as mentioned by De St. Joseph. The flap 

 of the inferior division forms an irregular semicircle, shorter from above downward than the 

 superior, but projecting further outward. The dotted bristles also constitute two series, 

 viz. a longer group with finely tapered tips, and a shorter series with shorter tips and indica- 

 tions of wings. The upward slope of these bristles is less than in the case of the dorsal. 



Little change can be recorded at the twenty-fifth foot (Plate XCVII, fig. 2 a) except 

 that the vertical diameter of the inferior lamella or flap has increased and in some a 

 papilla has appeared on its upper edge, whilst its transverse diameter has diminished. 

 Considerable variation would appear to exist in examples from different localities. Thus 

 Mesnil describes the alteration of the ventral lamella as occurring at the twenty-fifth 

 bristled foot, but the change took place behind this in the British forms, and the foot 

 figured by the French author as representing the incipient stage is the thirty-seventh. 



