NOTE ON A NEW SPECIES OF THE GENUS NAIS. 385 



less regular than in N. elinguis, or Bohemilla, or Pa- 

 ranais, but more regular than in N. josinse. One very 

 peculiar feature, hitherto unrecorded, I believe, is the con- 

 nection which exists between the branch d, in Somite v, and 

 the ''commissural^ vessel e in Somite vi, which connects 

 the dorsal and ventral trunks ; the branching of this com- 

 missural vessel is also peculiar. The shape of the brain is 

 utilised by Vejdovsky for determining species, therefore I 

 have appended a figure of this organ in N. heterochseta 

 (fig. 5) ; it will be seen to resemble somewhat the brain of N. 

 jo sin 86 (Vej., Taf. ii, fig. 28) in the constriction of the 

 anterior lobes from the posterior, but in N. heterochseta 

 this is more marked, and at the same time the shape of the 

 posterior lobes is different. 



With regard to the gut, the "stomach," or dilatation in 

 Somite viii, is not nearly as marked as in other species, and 

 more nearly resembles that in Paranais littoralis.^ 



The pigmented covering of chloragogic cells commences in 

 Somite vi, and is continuous thence throughout the body till 

 quite near the posterior end. 



The nephridia present the peculiarity which has scarcely 

 been sufficiently insisted upon by recent writers, though it has 

 been recorded by Carter" and by Timm,^ that very usually 

 there is in Naids only a single nephridium in some or all the 

 somites. In the present species there is never more than one 

 nephridium per somite ; the nephridium is very long, and fre- 

 quently the coiling tube occupies two somites, communi- 

 cating by means of a funnel with a third somite (fig. 4). In 

 this case, then, there is one nephridium in the place of four 

 (a pair in Somite xi and a pair in Somite xii). In most of the 

 somites the nephridium lies on the animaPs right side. So 

 far as I have been able to observe, in the living animal there 



^ See A. G. Bourne, " Notes ou Naidiform Oligochseta," ' Quart. Journ. 

 Micr. Sci./ xxxii, PI. XXVI, Qg. 2. 



2 " Spermatology of New Species of Nais," 'Ann. Mag. Nat. Hist.,' ii, 

 1858, p. 1. 



3 " Beob. lib. Phreoryctes uud Nais," ' Arb. aus Zool. Inst. Wurz- 

 burg,* vi, 1883. 



