414 EDWIN S. GOODRICH. 



(8) has mentioned this worm in a paper on the fauna of 

 Madeira, and Fraipont has made a detailed study of its 

 nervous system (3). 



External Characters. — I have nothing to add concern- 

 ing the external morphology of Saccocirrus, excepting v^^ith 

 regard to its parapodia and chaet^. Unlike what has been 

 described by Marion and Bobretzky, the parapodia in my 

 specimens do not extend all the way from the second^ to the 

 last segment; but there is at the posterior end of the animal 

 a variable number of segments (from ten to twelve), on which 

 neither parapodia nor chsetsB are present. The transition 

 fi'om the region with parapodia to the region without is 

 marked by one or two segments in which the parapodia and 

 chgetae are rudimentary. In every bundle of ch8eta3, besides 

 the oi"dinary chaetBe described with blunt ends, I find one 

 long needle-like cheeta, the tip of which is divided into three 

 sharp prongs (fig. 9). 



It is of course possible that the Saccocirrus of Naples is 

 not of the same species as the worm described by Marion 

 and Bobretzky from Marseilles ; but on the whole this seems 

 unlikely, since Saccocirrus papillocercus has also been 

 found in the Black Sea by its original describer, and at 

 Madeira by Langerhans. The discrepancies in the descrip- 

 tions may vanish on a closer inspection of specimens from 

 the other localities. 



Nervous System. — It is well known that the central 

 nervous system consists of a brain in the prostomium, from 

 which two nerve-cords run along ventrally above the epi- 

 dermis on either side of the body. Fraipont also found, 

 extending along the oesophagus, two strands, which he con- 

 jectured must be of nervous nature, although he was unable 

 to follow them to the brain. In my series of sections these 

 two nerves can be plainly seen to arise from the ventral sur- 

 face of the brain, more towards the middle line, but quite 

 near to the origin of the main nerve-cords (fig. 2). They 

 pass backwards along the roof of the buccal cavity (fig. 16) 

 ' The " first ses:meiit " is probably formed of two fused segments. 



