CASTALIA FUSCA. 129 



in April it is possible that it may have been connected with the development of the ova. 

 Sir J. Daly ell, again, noted that the finest examples were scarlet, though some were 

 yellow, but that the colour depended on the food. 



The proboscis (Plate LVIII, fig. 16) is short, firm, cylindrical, the circular aperture 

 in extrusion being surrounded by a dense fringe of filiform papillae. It has two thickened 

 ventral edges, which are simply the thickened parts of the organ in protrusion. The whole 

 organ is firm, and well adapted for predatory habits. Dr. Gr. Johnston found that they 

 devoured each other in confinement, and Sir J. Dalyell fed them on mussels. The latter 

 author thought that the colour of the body was dependent on the food, but more probably 

 it is due to the development of the reproductive elements. Intestine richly ciliated. The 

 feet are prominent throughout, stretching, with the bristle-tufts, outwards more than 

 the diameter of the body. Though apparently uniramous they are really biramous 

 (Plate LXIX, fig. 16), for two small spines pass to the base of the dorsal cirrus, which is 

 the only representative of the dorsal division. The ceratophore of the cirrus is both 

 large and long, and the cirrus itself is very long, and is slightly tapered from the base 

 towards the tip. Articulations are visible some distance above the base, and are very 

 marked towards the tip. The setigerous lobe is massive, with a bluntly conical 

 extremity, the tip being formed by a blunt papilla into which the spine goes, and another 

 occurs a little above it ; while the ventral cirrus, which is comparatively short, unjointed, 

 and little tapered, leaves the foot internal to the bristles, which project between a 

 posterior flap and the papillae in front. The shafts of the bristles (Plate LXXVIII, 

 fig. 4) are boldly curved towards the tip, are yellowish, striated longitudinally, except at 

 the tip, where the striae are oblique, and marked by fine transverse striae. The end of 

 the shaft is not much dilated and is bevelled to a shoulder, which is slightly bifid and 

 gives attachment to the terminal blade. The upper end of the bevelled region is also 

 bifid. The distal process is longest in the middle of the series, shorter superiorly and 

 inferiorly, and ends in a curved claw with a secondary process beneath. The edge of the 

 blade has minute serrations at the base, then a series of larger curved teeth, followed 

 again by small serrations which diminish and disappear before the tip is reached. Filmy 

 algae grow from the tip of the shaft and the terminal blade. 



Reproduction. — In May, when carrying ova, the body assumes a fine mauve or 

 purplish-pink hue, which extends from the posterior region of the proboscis to the tail. 

 In confinement the ova are discharged by rupture of the body, which then assumes the 

 ordinary hue. The ova are pinkish and show a zona with markings externally. They 

 were probably unripe. The scarlet specimens alluded to by Dalyell may have carried 

 ova. Females with advanced ova are found at Plymouth in April (Allen). 



Habits. — It swims gracefully and actively through the water with an undulating 

 motion, its cirri streaming from the sides, but if irritated it discards these organs, and 

 even (as in spirit) breaks into fragments and throws off its feet. According to Bohn, 1 

 the movements of this species are in accord with those of Eulalia, but its activity and 

 irritability are quite distinctive. 



This species was first found by Dr. Johnston, who afterwards confounded it with the 

 Gastalia punctata of CErsted, nor did Claparede and others notice the difference between 

 1 Much of the literature of the subject has escaped this author. 



74 



