188 POLYCIRKUS'. 



preservation, swollen anteriorly, and tapering posteriorly to the aims. Median tongue- 

 shaped ventral scute behind the mouth, and seven to eight pairs of closely-arranged 

 scutes immediately behind. Ventral surface grooved throughout. Colourless blood, 

 but with heart (fourth to fifth segments). Setigerous processes commence on the 

 second or third segment and number thirty to sixty, but cease before reaching the 

 posterior end. Bristles long, translucent, and tapering from the base to the slender, 

 curved, and finely serrated tip, devoid of wings, and in two series — longer and shorter. 

 Uncinigerous processes either absent anteriorly, or begin on the ninth bristled segment 

 (fifteenth segment — Ssolowiew) and continue to the end. Hooks avicular, with elongated 

 base, slightly curved, with a process beneath the main fang and a single tooth above it. 

 Anterior nephridia larger than the posterior. Tubicolar, often in fissures of rocks. 

 The genus is widely distributed. 



De Quatrefages 1 (1844) found no circulatory organs in this Group (his Apneumea), 

 the fluid in the coelomic cavity performing the function of this system, driven, as he 

 supposed, by a system of "palettes microscopiques," composed of a series of vibratile 

 cilia on the wall of the perivisceral cavity at the base of each foot. Though this 

 explanation needed subsequent correction, the author for the first time described the 

 absence of blood-vessels, as in the Grlyceridse and Capitellidas. 



Claparede 2 (1864), in his remarks on the genus Aphlebina of De Quatrefages, pointed 

 out that the interpretation of that author as to the movement of the coelomic fluid was 

 erroneous, for no cilia could be observed in the living forms. He was of opinion that 

 the movement of the fluid was clue to the remarkable muscular contractions and 

 dilatations of the body as in other anangian forms, such as Glycera and Capitella. The 

 Swiss author further gave a general account of the structure of the group, mentioning 

 two new species, viz. A. hsematodes and A. pallida, the latter, however, probably pertaining 

 to a known form. Notwithstanding the foregoing statement concerning the movement 

 of the perivisceral fluid, Claparede 3 at a later date (1868) describes the perivisceral 

 cavity of Polycirrus caliendrum as covered with cilia. 



The same author subsequently (1868) gave the following classification of the 

 group : 



a. With setigerous processes and tori uncinigeri. 



a. Uncini avicular. 



a. Dorsal bristles throughout the body — Aphlebina, De Quartref. ; Ap- 



neumonea, De Quatref. ; Polycirrus, Mgrn. 

 f3. Dorsal bristles in the anterior region only — Polycirrus, Grube (non Mgrn.). 



b. Hooks sublinear, aciculiform — Am&a (Mgrn.). 

 13. With dorsal bristles ; no hooks— Lysilla, Mgrn. 



The only species of Pohjcirras mentioned is P. caliendrum from Naples. 

 Gravier, 4 who founded a new genus Anisocirrus, for a Polycirrid from the Red 

 Sea, thus distinguishes the genera : 



1 'Ann. Sci. Nat/ (3) I, 1844, p. 18. 

 3 f Grlanures Zoot./ pp. 24 et seq. 



3 ' Annel. diet./ Naples, p. 406. 



4 'Nouv. Arch. Mus. Paris/ 4 e ser. ; t. viii, p. 231. 



