372 
Proceedings of the Royal Society 
3. On the Arrangement and Relations of the Great Nerve- 
Cords in the Marine Annelids. By W. C. MTntosh, M.D., 
F.R.S.E., F.L.S. 
(Abstract.') 
Fam. Eupiirosynid^:. — In Euphrosyne foliosa , Aud. and Ed., the 
separate nerve-cords are comparatively large, and lie quite within 
the body-wall, the oblique muscles, which generally bound the 
longitudinal ventral muscles, decussating beneath them. 
Ampiiinomidas. — The cords are somewhat small and flattened 
in Chloeia , and occupy an area bounded internally by a trans- 
verse band of fibres, and externally by the circular muscular layer 
and the hypodermic basement-tissue. The oblique muscles 
are attached at the outer border of each trunk. 
ApiiRODiTiDjE. — The nerve-cords in Aphrodita aculeata , L., occur 
in a transversely elongated space between the ventral attachments 
of the oblique muscles, and bounded externally by the hypodermic 
basement-tissue and the cuticle. In Hermione Jiystrix , Sav., again, 
they lie — as distinct trunks — in a well-defined hypodermic area 
within the dense cuticle, and separated by an interval from the 
attachment of the oblique muscle on each side. 
Polynoidje. — In Lepidonotus squamatus , L., the cords occupy a 
hypodermic area between the ventral longitudinal muscles. The 
oblique muscles pierce the vertical at the upper and outer angle of 
the space, and are attached to the hypodermic basement-tissue, 
external and superior to the cords. A belt of hypoderm intervenes 
between the latter and the cuticle. In Polynoe scolopendrina , Sav., 
the interval between the ventral attachments of the oblique muscles 
is less, and the cords are bounded superiorly by a special longitu- 
dinal muscle. 
Accetid.e. — In Panthalis (Erstedi , Kbg., the trunks are situated 
in the hypodermic region between the ventral longitudinal muscles, 
a thin layer of the former tissue occurring between them and 
the cuticle. The great oblique muscles pass down to their 
upper and outer border. The space between the ventral longitu- 
dinal muscles is less than in the Polynoidae. 
SiGALiONiDiE. — The space between the ventral longitudinal 
muscles anteriorly in Sthenelais boa , Johnst., is still more narrowed 
