SYLLIS GRACILIS. 205 



The ventral lobe is also shorter and distinctly tongue-shaped, being narrower at the base 

 and tip than in the centre. 



The middle region of the body is characterized by the great development of the strong 

 bifid bristles, 1 two of which are present in each foot (Plate LXX, fig. 25 a), the jointed 

 bristles having disappeared. The strongest of these have no intermediate teeth in the 

 fork, others present a single oblique spike, while a few have more than one point. Many 

 have no distinct points though the fork is slightly rough. These two strong bristles 

 continue to the posterior third, where a tendency to the development of a separate spur- 

 like process, instead of a limb of the fork, occurs. This is generally better marked in one 

 than in the other (of the two in each foot) . 



In the posterior feet (about the posterior fourth) a single strong bristle occurs in the 

 centre, the end of its shaft is bevelled, and a stout terminal piece is appended, the tip of 

 which is generally indistinct. It is flanked on each side by nine bristles of the type of 

 those in front, viz., with a long terminal piece bifid at the tip. The stout bristles of the 

 feet behind the foregoing segments gradually disappear, the first and then the second, 

 until only jointed bristles remain, one of which, however, is stouter than the others, 

 and has a shorter terminal piece. Finally in the last twelve or more segments only 

 the slender bristles with the elongated and bifid terminal pieces are found. 



In an example from Plymouth eight segments, and the cirri of the tail, were in 

 process of reproduction. 



Claparede (1864) 2 describes the spines as having a button-like tip as in $. Armandi. 

 He found a papilla between the caudal cirri, as in certain other species, and mentioned 

 that the blood, usually colourless in Syllids, is in this species of a beautiful rose colour. 



This author 3 mentions that the term Syllis gracilis was first used by Delle Chiaje, but 

 as the species is indeterminable Grube's name stands. The same term was adopted by 

 Schmarda for a species from the Cape after Grube had employed it. He drew special 

 attention to the glands with coiled contents near the dorsal cirri, and to the coiled 

 structures in the latter. 



Langerhans (1879) adds an interesting note on the arrangement of the bristles 

 (simple, mixed, and compound) in the various segments of this species, but it is not con- 

 stant in the several examples. He thought the stolons had the form of Ioida. 



De St. Joseph (1886) found his example at Dinard in the midst of Cynthia glomerata. 

 He describes the proboscis as elongated, stretching from the second to the eleventh 

 segment, the conical tooth in front with a poison canal. The proventriculus extends from 

 the twelfth to the fifteenth segment. He criticises Czerniavsky, who made four species 

 out of it in the 'Fauna of the Black Sea ' (Mare Ponticum). In his later note (1895) he 

 adds further information. He observes that the first twenty-seven segments have bristles 

 with a long bidentate terminal piece, whereas from the twenty-eighth to the forty-fourth 

 segment these are replaced by two stout bristles with a forked point (ypsiloide), with 



1 Claparede states that the ypsiloid bristles commence from the nineteenth to the twenty-sixth 

 segment. ( Annel. Nap./ p. 194. 



2 This author thinks the species approaches Syllis oblong a, Keferstein, and S. tigrina, Rathke,, 

 though they differ in palpi and bristles. ( Beobach./ pp. 52 and 82. 



3 ' Annel. Nap./ p. 193, etc. 



