378 Proceedings of the Royal Society 
the homologues of the ventral longitudinal are pushed outward. 
The oblique preserve their usual relations with the latter and the 
nerve-cords, over which their ventral termination occurs. Another 
muscle, probably the homologue of the transverse, passes from the 
termination of the oblique inward to the middle line on each side. 
As the late M. Claparede has shown, the cords approach each other 
in the posterior region in Chcetoyterus , while in Telepsavus they re- 
main separate throughout.* 
SpioniDjE. — As pointed out last session,! the cords in this family 
are hypodermic in position. Their relation to the ventral inser- 
tions of the oblique muscles are also well shown, since they follow 
the latter in their gradual progress inward from the sides of the 
body in front until the cords touch and the muscles meet over 
them. The neural canals are largely developed. 
CirrattjliD-ZE. — In Cirratulus cirratus , 0 . F. Muller, the cords in 
the anterior region lie in the median line ventrally within a thick 
hypodermic area. The oblique muscles are inserted at the summit 
of the area, and the sides of the ventral longitudinal muscles over- 
lap its upper arch. The circular muscular coat is continuous over 
(internal to) the cords. In Dodecaceria concharum , (Erst., a thick 
median mass of blackish hypoderm protects the cords, and the 
relations of the oblique and longitudinal ventral muscles are 
similar. 
Halelminthid^;. — This family approaches the Lumbricidse in hav- 
ing the nerve-cords placed within the great and nearly continuous 
longitudinal muscles of the body-wall. Externally (in the ventral 
region of Gayitella capitata , Fahr.) are in addition a dense circular 
muscular coat, a thin layer of longitudinal fibres, basement-tissue, 
hypoderm, and cuticle. Anteriorly there are two divisions of the 
ventral longitudinal muscular fibres under the nerves, but in the 
middle region of the body they have coalesced into a single mass. 
A neural canal occurs superiorly in the ovoid nervous area. Two 
vertical muscles bound those above which the nerves lie, but the 
oblique are not recognisable. 
Maldaidn^;. — In the anterior region of Praxilla yrcetermissa , 
Mgrn., the nerve-cords lie beneath (outside) the circular muscular 
*Annelides Sedent. p. 127, &c. 
t Proceed. R.S.E., vol. ix. No. 94, p. 124, &c. 
