CELETOPTERUS VARIOPEDATITS. 127 



the same shape, the outer edge showing an inward curve and then a convex portion, 

 from which it tapers distally. The bristles are enclosed in the process, which assumes a 

 slightly angular outline when seen from the tip. These organs are muscular, and perform 

 various movements, while they are likewise very sensitive. All show a characteristic 

 curve dorsalward. 



The ventral lamellas bearing the hooks undergo even more marked changes posteriorly, 

 the lateral flap appended to the side of the dorsal becoming short and almost filiform, 

 leaving the side of the dorsal process, and being appended to its base in front, the pads or 

 flaps for the hooks on the ventral surface being small. 



The posterior region has twenty-two or twenty-three strongly-marked segments, 

 each of which has a prominent dorsal division of the foot formed on the plan of the 

 great wings of the tenth segment, viz., a large fleshy lobe somewhat tapered distally and 

 enclosing a series of long and strong bristles tapered at both ends, but with the distal 

 most attenuate, indeed of the type seen in the tenth bristled segment. This process ends 

 in a ventral enlargement carrying on its anterior edge a band of hooks each of which 

 has about ten teeth. Besides, on the ventral surface are the two flaps bearing hooks 

 with ten or eleven teeth. Altogether there are thus four rows of hooks in each segment, 

 and the hooks individually vary little in the several rows. The dorsal divisions gradually 

 diminish posteriorly, and end in two small and somewhat lanceolate processes on each 

 side, below the level of the anus. 



The tubes are composed of a tough secretion which hardens into a leathery case 

 which is spindle-shaped, being wide along the greater part of its length, but narrowed 

 toward the finished opening at either end, and it is strengthened externally by fragments 

 of shells, algae, stones, mud, and other debris. Internally it is smooth. Its width enables 

 the annelid to reverse itself, so as to make the finished apertures at the ends. Some large 

 tubes are 8-g- to 9 inches long. Occasionally the tubes are feathered with Obelia and 

 other zoophytes (Plate XCVIII, fig. 7), or bound in a mass of Cellepora and Serpidse, with 

 adherent Ascidians, nullipores, young Balani, fragments of shells, and Spatangi, amidst 

 the crevices of which Ophuiroids and small annelids lurk, and on the flat surfaces of which 

 Lepraliae spread their net-work of lace. Some tubes are mostly protected by broken 

 shells and often bent like a siphon. Shells, stones, and fragments of Balani were common 

 on the tubes between tide marks at Herm. 1 



It is most beautifully phosphorescent, bright flashes being emitted from the posterior 

 feet, but the most vivid light occurs on the dorsum between the great sickle-shaped lobes 

 which curve forward over the first region of the body. Here the phosphorescence is 

 intense, and the copious mucus exuded by the animal can be drawn out as vivid bluish- 

 purple fire which, besides, now and then gleams along the edges of the wing-like flaps, 

 illuminating the water around. This point, moreover, seems to be the last to show the 

 phenomenon when the specimen is moribund. The bluish-purple light seemed to approach 

 that of burning potassium, and an odour resembling that of phosphorus was felt during 

 the experiments. The tough secretion hardens into a firm, whitish mass in spirit. 



1 Mr. Orton states that at Plymouth a specimen not thirteen months old constructed a tube 

 14 cm. long, and had developing ova in its gonad, f Journ. M. B. A./ vol. x, p. 316, 1914. 



