OWENIA FUSIFORMIS. 359 



each side with a groove running a short distance backward and nearly opposite the 

 interval between the median and ventral branchiae. A transverse patch of brown 

 pigment marks the collar dorsally, and passes to the eye-spot on each side, from which it 

 slopes to meet its fellow of the opposite side in the mid-ventral line about the level of the 

 first bristle-bundles. Drasche and Watson show that this pigment indicates the position 

 of the brain and oesophageal commissures which unite to form the ganglion from which 

 the ventral cord, which is devoid of ganglia or neural canals, arises. 



The body varies from 30 to 60 mm. in length, is firm and rounded anteriorly, some- 

 what flattened and tapered posteriorly, where it ends in a slightly bilobed tip, with the 

 anus in the centre ; the condition perhaps being more accurately described as a papillose 

 anus with a dimple in the centre dorsally and ventrally. The segments, which are 

 indistinctly defined, are from twenty-three to thirty in number, and vary remarkably in 

 antero-posterior diameter. The first region of the body, which commences with the 

 madder-brown collar, consists of the buccal and three bristled segments, as pointed out 

 by Kolliker in 1864, and the author in 1869, and not of two, as Grube, Claparede and 

 Lo Bianco supposed, the smaller posterior pair, which is more dorsal in position, having 

 been overlooked, or, as Claparede states, is the dorsal fascicle pertaining to the first pair 

 of tori. These bristles have a fine, pale, golden lustre, and the row or tuft stands more 

 or less vertically, the longest and most finely tapered being dorsal. All are simple 

 tapering bristles (Plate CX, fig. 9), and the pinnate spikes slant upward — that is, toward 

 the tip. The first pair is lateral in position and is about equidistant between the collar 

 and the second pair, with which it agrees in general arrangement. The third pair is not 

 visible from the ventral surface, being dorsal in position ; it springs a little in front of the 

 segment-junction, and is directed obliquely upward and outward. Its bristles have the 

 same structure as those in front, but the function probably differs. 



Dorsally the anterior region presents a long, shield-shaped central area, the broad 

 part of which is in front, and the sides are outlined by two frilled hypodermic bands, 

 which pass to the front of the third segment. Ventrally immediately behind the mouth 

 is a triangular area, specially alluded to by Mr. Arnold Watson, bounded by the line of the 

 nerve-cords, which slant inward from each side to form the fused central band along this 

 surface to the tail. 



A septum divides the buccal from the following segment, but the three bristled 

 segments form a single chamber. Each of the segments of the posterior region — that is, 

 after the third bristled segment — is separated from the adjoining one by a septum (Watson). 



The oesophagus is about the length of the anterior region, and is followed by the 

 intestine, which passes to the anus, a series of enlargements and constrictions occurring 

 during its course. De St. Joseph describes the colour of the canal in the third and fourth 

 posterior segments as greenish from glands. The gut has a dorsal and a ventral 

 mesentery. It is surrounded by the dorsal blood-vessel throughout the greater part of its 

 length, thus forming a peri-intestinal sinus (Watson). This bifurcates anteriorly near the 

 branchial region, bends downward, and unites with its fellow to form the ventral vessel, 

 which has numerous round ampullae, as many as forty occurring in the third posterior 

 segment (De St. Joseph). 



There are six, sometimes seven, pairs of cylindrical, rigid, thread-secreting glands of 



