138 BULLETIN OF THE 



the characters in synoptic form. The original description (Verrill, '79) 

 has been followed as closely as was compatible with the changes necessi- 

 tated by the discovery of the female, and by a more perfect acquaintance 

 with the anatomy of the male. 



Nedonema, Verrill, char, emend. — Body long, slender, nearly round. 

 Cuticula finely ringed, on the median lines often deepl}^ infolded and 

 bearing on each line two rows of hair-like bristles. Bristles hollow, 

 superficial and unconnected with each other. Head without appen- 

 dages, obtusely rounded or bluntly conical with a shallow dorsiventral 

 furrow on its anterior aspect. Mouth-opening in the centre of this fur- 

 row, minute. In the male the tail is curved ventrad, and terminates in 

 a small conical intromittent organ. Female smaller, the posterior end 

 slightly enlarged, abruptly truncate, with terminal vaginal (?) opening. 

 Alimentary tract rudimentary and anus wanting in both sexes. 



Nedonema agile, type species. — A long, slender, and exceedingly 

 active round worm, resembling in form and motions a Gordius, found 

 swimming at the surface of the sea with a rapid undulatory motion. 

 Integument firm, opaque, smooth, except for many minute circular ridges 

 interrupted at the median lines, which are themselves often thrown 

 into larger, deeper folds, locally very prominent. Body in life round, of 

 nearly uniform size throughout, tapering slightly close to the head, and 

 somewhat more towards the posterior end in the male. Each median 

 line is distinguished by two narrow longitudinal bands of minute dots 

 between which stand two longitudinal rows of hair-like bristles. The 

 worm undergoes torsion in the anterior third of the body, so that the 

 median lines appear lateral in the posterior two thirds of the body. The 

 double row of bristles extends from a point 1 or 1.5 mm. behind the apex 

 of the head to about the same distance from the posterior extremity of 

 the body. The bristles are 0.3 mm. in length, opposite to each other, 

 hollow, unconnected by any web, entirely superficial, and hence easily 

 detached and often injured or lost over considerable stretches of the 

 body. The head is marked anteriorly by the presence of a shallow 

 median dorsiventral furrow, on each lateral edge of which are one, some- 

 times two, low rounded papilla?. The anterior portion of the body is 

 semi-transparent, externally not separated by any constriction from the 

 rest of the body ; but internally an anterior chamber is divided from the 

 general body cavity by a partition which is concave anteriorly. The an- 

 terior chamber is traversed by the oesophagus, and contains ventrally the 

 brain, while the dorsal space is filled by four large conical cells which 

 send processes down into the nervous matter of the brain. The oesopha- 



