Gathj Marine Laboratory, St. Andreas. 163 



defined, are from 23-30 in number, and vary remarkably in 

 antero-posterior diameter. The first region of tbe body, 

 which commences with the madder-brown collar, consists of 

 the buccal and three bristled segments, as pointed out by 

 Kollikcr in 1 8G4- and the author in 1869, and not of two as 

 Grube, Claparede, and Lo Bianco supposed — the smaller 

 posterior pair, dorsal in position, having been overlooked 

 or, as Claparede states, represents the dorsal fascicle per- 

 taining to the 1st 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 and the pinnate spikes 

 slant upward — that is, toward the tip. The first pair of 

 bristle-bundles 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, 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 outlined by two frilled bands which pass to the front 

 of the 3rd 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 frorn the following segment, 

 but the three bristled segments form a single chamber. 

 Each of the segmeuts of the posterior region (that is, after 

 the 3rd 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 3rd and 4th posterior segments as greenish from 

 glands. The gut has a dorsal and a ventral mesentery and 

 passes through the septa. 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 processes, bends downward and 

 unites with its fellow to form the ventral vessel, which has 

 numerous round ampullae, as many as forty occurring in the 

 3rd posterior segment (De St. Joseph). 



