ARCHIANNELIDA 



281 



Fig. 449 



Larva of 



Pohigordius 



appendiculatua 



(Cowles). 



which have no parapodia and usually no segmental setae; head com- 

 posed of prostomium and metastomium, the former lying in front of 

 the mouth and bearing a pair of tentacles, the latter larger than the 

 prostomium and without appendages; body cavity, 

 digestive, excretory, and vascular systems typically 

 annelidan in character; nervous system subjacent to 

 the hypodermis and without distinct ganglia; animals 

 unisexual, the genital products developing from special- 

 ized regions of the peritoneum during the breeding 

 season; young born as trochophore larvae: 2 or 3 

 genera ; the larvae are common in the plankton at many 

 places along the Atlantic coast, but with the exception 

 of Ch&togordius no adult worms have been found. 



1. POLYGORDIUS Schneider. Body filiform; segmentation indistinct 

 at the forward end but more distinct at 

 the hinder; tentacles short; anal segment 

 enlarged: about 6 species. 



P. appendiculatus* Fraipont (Fig. 

 449). Length 20 mm.; body salmon color; 

 2 long anal appendages present: Atlantic 

 coast (only larval forms heretofore 

 found) ; Mediterranean. 



2. CH^TOGORDIUSJ Moore. Segmenta- 

 tion as in Polygordius; hindermost 10 or 

 12 segments setigerous; no anal enlarge- 

 ment: 1 species. 



C. canaliculatus Moore (Fig. 450). Length 30 mm.: among marine 

 oligochaets on Cape Cod. 



CLASS 2. CILETOPODA4 



Segmentation distinct, except in the Echiurida, both internally and 

 externally; setae segmentally arranged in groups on the parapodia, where 

 these are present, or sunk in pits on the integument: 3 orders. 



* See "On the Rearing of the Larvae of Polygordius appendiculatus and the 

 Occurrence of the Adult on the Atlantic Coast of America," by R. P. Cowles, Biol. 

 Bull., Vol. 4, p. 125, 1903. 



t See "A New Generic Type of Polygordius," by J. P. Moore, Am. Nat., Vol. 38, 

 p. 519, 1904. 



% See "Annelida Chaetopoda of New Jersey," by H. E. Webster, Thirty-second Rep. 

 N. Y. St. Mus. Nat. Hist., p. 128, 1879. "New England Annelids," by A. E. Verrill, 

 Trans. Conn. Acad., Vol. 4, p. 285, 1881. "The Annelida Chsetopoda from Province- 

 town," etc., by H. E. Webster and J. E. Benedict, Rep. Com. Fish, for 1881, p. 699, 



1884. "The Annelida Chaetopoda from Eastport, Maine," by same, same jour, for 



1885, p. 707, 1887. "The Annelida Chaetopoda of Beaufort, N. C.," by E. A. Andrews, 

 Proc. U. S. Nat. Mus., Vol. 14, p. 277, 1891. "Polychseta of the Puget Sound Region," 

 by H. P. Johnson, Proc. Bost. Soc. Nat. Hist., Vol. 29, p. 381, 1902. 



Fig. 450 Chcetogordius cana- 

 liculatus (original drawings by 

 J. P. Moore). A, anterior end; 

 B, posterior end. 



