phorescence appears to be less vivid during severe weather and when confined for a night
or two in shallow vessels—a feature probably due to nervous prostration, or it may be
associated with approaching maturity. Specimens placed in a weak solution of picric
acid in sea water are not luminous, and the scales are not at first thrown off.
Parasites.—The crustacean parasite Herpyllobius arcticus? Stp. Ltk. (Silenium
Pólyno'èSy Kr.), occasionally occurs in arctic examples attached to the dorsum. Levinsen
also found another crustacean parasite, viz. Selioïdes Bolbroei, Lev., on one from
Greenland.9
On the dorsum, under the scales of a specimen from the tidal region at Balta
Sound, Shetland, numerous examples of a fine Loxosoma in various stages of growth are
found.
A peculiar warty growth appears on the tentacular cirrus of an example from the
Gulf of St. Lawrence, and a series of minute whitish tubercles in an arctic example from
Bessels Bay.
The bristles harbour many parasitic algas, besides mud, foraminifera, and sponge-
spicules. At St. Andrews a small Sabella, Syllis, and Pholoë have been found amongst
the bristles, and young mussels occasionally fix themselves to the dorsal bristles.
A translucent Ascaris, fully half an inch in length, occurred in the peri-pharyngeal
space of a female. The slightly truncated snout showed one or two blunt papillae, while
the pointed posterior end had a few acute papillae. Though outside the gut it had free
access to the perivisceral fluid, and, moreover, the long anterior caeca passed forward on
each side of the space.
Development.-^The broad outlines of the development of this species have been
known for a considerable time, and it may therefore form the type for the group.
Comparatively small species are occasionally found mature, or carrying ova under the
scales. Michael Sars,8 as early as 1845, described the occurrence of ripe examples of
Sarmothoë in February and March. He noticed the mature females exhibited a chancre
of colour, becoming pale rose behind the anterior fourth. This was due to the eggs
which covered the dorsum. He thought that the ova passed out by a small apérture
above the feet. He watched the development of the egg from early segmentation to the
movement of the embryo by cilia, and its slightly greenish coloration. The larvae
(monotrochous trochophores) escape after two weeks, swim freely, and bear two eyes,
with a pre-oral band of cilia. Max Müller, Desor, and others have also described the
development. Desor, however, fell into the error of supposing that thé larva escaped
from a similar ciliated investment to that of Lineus obscurus.
Max Müller,4 in the young of either this or an allied form, .pointed out that new
segments were interpolated posteriorly. He described the dimorphism of the bristles,
1 *Kgl. Danske vidensk; Selsk. Skrifter naturv.-mathem. afd./ Bd. v, 1861; and Kröyer,
‘Naturh. Zidskr./ 3 die R., Bd. ii, 1863, &c.
2 ‘ Videnskab. Med. fra den nat., &c./ i Kiobenh., 1887.
8 “ Zur Entwicklung der Anneliden,” ‘ Arch. f. Naturges./ 11 Jahrg., v. 1,1845.; and ‘ Ann. Nat.
Hist./ 1845, p. 188 (vol. xvi).
4 “ Ueb. d. Entwicklung u. Metamorph. d. Polynoën,” ‘Müll. Archiv/ Jahrg. 1851.
the condition of the alimentary canal, and the development of the feet. His species
had two pairs of eyes.
Claparède1 gives the early stages of a Polynoë up to the formation of feet and
bristles. His example had eleven pairs of feet.
Viguier 9 refers to a pelagic Polynoë of sixteen segments, but which, he says, showed
no larval appearance. The feet and the ventral bristles are comparatively long. I t is
in all probability a post-larval Polynoë from the Bay of Algiers, as Marenzeller also
thinks.
Dr. W. Michaelsen8 describes a pelagic polynoid from Ceylon (Drieschia pelagica),
in which the foot is simple, with very long hair-like bristles, and only a few shorter
thicker forms. These apparently represent the ventral division of the foot, and only a
single spine is present. The tentacular cirri and dorsal cirri are very long.
Marenzeller4 gives an account of a pelagic form of twenty-four segments procured
by the Prince of Monaco, in 48° 50' lat. N., and 21° long. E. of Greenwich, under the
name of Nectochseta Grimaldii. It is characterised by the great elongation of the inferior
bristles. Scales absent, palpi and cirri smooth.
Fewkes5 described a young Polynoë with only three pairs of feet.
Too, little is yet known of the pelagic forms described by Michaelsen and Marenzeller
to speak with certainty of their precise relationships. The presence of only a single
spine and the simple nature of the foot in Drieschia are features which diverge from the
ordinary types.
Prof. Y. Hacker of Freiburg gave in 18966 the results of his studies of the larvæ of
Polychæta at Naples. In the Aphroditidæ he describes three stages of a Polynoë, viz.
the trochophore, metatrochophore, and nectochæte7 stages. In the Aphroditaceans
the trochophore moves at first by aid of its cilia, and then the bristles develop secondarily
and enable the post-larval stage to assume great activity during its pelagic life. His
species was probably Polynoë reticulata.
The ovaries of Harmothoe imbricata form a series of lobulated organs stretching
from the seventh foot (which has a segmental [nephridial] papilla, as has also the sixth)
to the posterior end. They are small anteriorly in the region of the proboscis, though
as a rule they do not reach this part, but attain in January a considerable bulk throughout
the rest of the body, again diminishing posteriorly.
The eggs become prominent in November, being coarsely granular, with a distinct
nucleus and nucleolus (Fig. 27)'. They seem to have a hyaline connecting substance,
to which perivisceral corpuscles attach themselves. They vary in size, the smaller being
1 ‘ Beobach../ 1-863, p.80, Taf. viii, f. 1—11.
2 ‘ Archiv. de Zool. exper./ vol. iv, 1886, p. 416.
3 I Jahrb. d. Hamburg. Wiss. An'stalt/ ix, 2, 1892, p. 6, figs. 15—18.
4 ‘ Bullet, de la Soo. Zoolog. de France,’ 1892, p. 173.
5 ‘Bull. Mus. Comp.Zool. Harv. Coll. Camb./ v, 11, 1883—5.
6 ‘ Zeitsch. f. w. Zool.,’ Bd. lxii, pp. 74—168, Taf. iii—v.
7 Njjx«r, swimming or pelagic; and x aiTri> bristle.