SPIONID^J. 135 



near the oesophagus. In Nerine and other Spionids the branchise have a single line of 

 cilia . 



The middle region of the body in Audouinia presents in section a ventral vessel, and 

 the dorsal is very large and contains a brown central mass. The two lateral vessels are 

 also large. The dorsal is surrounded by a sinus with a superior and inferior branch, 

 with which it is in direct communication. A transverse branch on each side passes to the 

 longitudinal lateral, from which branches go to the branchise. The blood is conveyed 

 from the branchiaB by a transverse trunk to the ventral vessel, and furnishes a rich series 

 of capillaries to the feet. The dorsal ends anteriorly in two large vessels supplying the 

 branchias and tentacles. A heart-body is present. The branchiae have both artery and 

 vein; the tentacles only a single vessel. 



In Andouinia filigera the nerve-cords are within and in contact with the circular 

 muscular coat. The cerebral ganglia are absent, and the two oesophagus connections 

 diminish rapidly in front. Each branchia in this form has two nerves, and so with the 

 tentacles. In Nerine cirratulus the nerve-cords are separate, and the single " tubular 

 fibre " lies between them, and passes below the transverse commissure. 



The Spionidas constituted the first and most typical family in Levinsen's l (1883) 

 Syllidiformia Spionina, but the divergent families which followed showed how difficult it 

 is to form large natural groups of the Polychseta. He placed Nerine, Scolecolepis, and 

 Aonides under the genus Spio. He grouped the genera as follows : Prionospio, Spio- 

 phanes, Polydora, Spio, Disoma, and Aonides — PxeilochMus being appended. 



Benham 2 (1896) considered that in the " Spioniformia " neither tentacles nor palps 

 are present, but that the peristomium carried two long tentacular cirri, and extended 

 forward at the side of the prostomium. He grouped under this sub-order the families 

 Spionidae, PolydoridaB, Chastopteridae, Magelonidas, and Ammocharidse. It is doubtful if 

 much can be gained by this association of the third and fifth families with the other three. 

 The sub-order fell under the branch Phaneorcephala " in which the prostomium retains its 

 ancestral condition as a lobe overhanging the mouth. " 



Leschke 3 (1902) gave an account of the pelagic larvse of Poly dor a ciliata, Spio 

 seticornis, and Nerine from the Bay of Kiel, accompanied by good figures. 



De St. Joseph (1894) describes and figures several larvae of Nerine. The earliest stage 

 resembles that figured by Claparede 4 and Fewkes 5 and has six or seven segments of the 

 body, and was several times found in the cup of a Campanularia. In the next stage the 

 head is better developed, tentacles are present, and the four eyes form a transverse row 

 on the head. The first body-segment has a long tuft of bristles on each side. The following 

 stage has seventeen segments of the body, but the long provisional bristles in front are 

 absent. There is no certainty that all belong to the same species. 



Haecker 6 (1896) mentions a metatrochophore of a Spio from Naples with six pairs 



1 'Vidensk.Meddel. Foren. Kjobenh./ 1883, p. 180. 

 3 c Polychaeta, Camb. Nat. Hist./ vol. ii, p. 303, et seq. 



3 ' Wissenschaft. Meeresuntersuch./ Bd. v, p. 113, Taf. vi, figs. 1 — 10. 



4 ' Beobacht. Thiere Normandie/ pi. viii, figs. 4 and 5. 



5 ' Bull. Mus. Comp. Zool./ t. xii, pi. ii, fig. 2. 



6 'Zeitschr. f. wiss. Zool./ Bd. lxii, pp. 89—91. 



