POLYCIRRUS. 



189 



Hooks 



Avicular 



Polycirrus, Grube. 



/Present in general in a certain number of 

 I thoracic segments. No tentacular collarette 

 | Absent on the thorax ; a large tentacular 

 ( collarette ....... Anisocirrus, Gravier. 



Aciculiform, absent on the thorax Amsea, Malmgren. 



.Completely absent on the thorax and abdomen . . Lysilla, Malmgren. 



De St. Joseph (1894), while following the classification of this group by Malmgren, 

 inclines to the subdivision of the genus Polycirrus into two genera or sub-genera, as 

 indicated by Langerhans, the one devoid of the thoracic hooks (without the accompanying 

 bristles), and having the abdominal hooks with the bristles, the other having the hooks 

 of both kinds. He mentions that even the parasites of the Polycirridea differ from 

 those of the Amphitritea, since Nematodes are frequent in the former, and he has also 

 found a scolex of a Tetrarhynchu's in the intestine. He points out that the alimentary 

 canal agrees with that of the Amphitritea, viz. a pale oesophagus, a yellowish glandular 

 stomach, followed by a chitinous stomach and a yellowish intestine. 



One of the most recent classifications of the Polycirrids is that of Prof. Caullery 1 

 (1916), who arranges them in two main groups, thus : 



a. Species without uncini in the segments with capillary bristles. Ex Ereutho 



smitti, Mgrn. ; Polycirrus medusa, Grube. 



b. Species with uncini in the region provided with bristles, and this is split into 



two subdivisions, viz. : 



B v Those with dimorphic uncini, appearing in segments 7 — 10. Ex. Poly- 

 cirrus aurantiacus, Grube ; P. caliendrum, Clap. ; P. denticulatus, De 

 St. Joseph. 

 b 2 . Those with uncini of one type, appearing in segment 13, and to which 

 are attached tendinous threads. Ex. Polycirrus hsematodes, Clap. 

 To the foregoing have to be added the genera Lysilla, Mgrn., and Hauchiella, 

 Levinsen, thus : 

 Uncini long ........... Amsea, Mgrn. 



Polycirrus, Grube. 

 Polycirrus, Mgrn. 

 Leucariste, Mgrn. 

 Ereutho, Mgrn. 

 Lysilla, Mgrn. 

 Hauchiella, Levinsen. 



„ short, avicular . . • . 



/ seventh to tenth segment 



Commencing \ at the thirteenth segment 



( after the setigerous segments 



. . f Some setigerous segments 

 No uncini .j AT . .,, 



( No bristles .... 



Fuchs' 2 (1907), in his description of the blood-systems of the Chsetopods, describes 

 the Polycirrids as devoid of branchiae and blood-vessels. The thorax has two unequal 

 chambers (a diaphragm occurring between the cephalic region and the second segment), 

 the anterior being the smaller. In the posterior chamber are the genital glands and 

 three pairs of segmental organs. 



In the Red Sea Dr. Crossland finds a species living without a tube amongst sponges 

 with a slight accumulation of fine mud. 



1 'Bull. Soc. Zool. France/ t. xl, p. 239. 



2 ' Jenaische Zeitsch./ 42 n.f., Bd. xxxv. 



