1921.] Fauna of the Chilka Lake : Polychaeta. 607 



respiratory function. They are not, however, supplied with blood-vessels as in 

 Dendronereis. The filaments have an ill-defined central lumen (fig. 6g). Morpho- 

 logically they appear to represent the proliferation of the dorsal ligule. 



A remarkable glandular organ occurs in most of the feet. They first appear in 

 the 14th setigerous segment, and continue to the end of the body. This distribution 

 shows that they have no functional connection with the branchial filaments. At 

 first they are small, but they rapidly increase in size. They lie in the upper part of 

 the foot, and open to the exterior just beneath the dorsal cirri. Their usual shape 

 and position is shown in figs. 6f, 6h, and 6j. Each consists of a number of elongate 

 cells with granular contents, the whole being surrounded by a thick muscular coat. 

 There is no common duct to the gland, and all the elongate cells apparently open to 

 the exterior through the thickened lip of the gland. In the middle and posterior seg- 

 ments the gland decreases considerably in size, and consists only of a few elongate 

 cells with a very thin muscular coat. In the segments where the glands occur, the 

 nephridia are very large, with many black granules in the duct cells. The nephridia 

 occupy most of the cavity of each foot, and are closely surrounded by branched 

 blood-vessels. 



In many respects this species is one of the most aberrant of the Nereids. The 

 parapodia are very heterodox in structure, and it is difficult to homologise the various 

 lobes. One of the most remarkable features is the presence of only a single lobe 

 beneath the ventral setae. This may be either the ventral ligule or the ven- 

 tral cirrus. As the latter is a much more constant structure than the former, it is 

 highly probable that this lobe is the ventral cirrus, and that the ventral ligule is 

 absent. As already mentioned, the dorsal lobe in the ist and 2nd feet may be either 

 the dorsal or median ligule. In all the other feet the median ligule is present. The 

 dorsal ligule is absent at least after the 29th foot. 



Habitat. — In brackish pools, salt lakes, Barantolla, near Calcutta. The salinity is 

 very variable, but never high, probably never exceeding sp. gr. 1.015 at 25°C. The 

 specimens were collected in November. 



Family NEPHTHYDIDAE. 

 Nephthys polybranchia, sp. nov. 

 (Plate XXIV, figs.iiA-G, and text-figs, na-b.) 

 Twelve specimens of this species were taken in Chilka Lake. They were all 

 approaching maturity, full either of ova or sperm. One specimen was 22 mm. long, 

 and had 52 setigerous segments. Another was 19 mm. long, with 50 setigerous seg- 

 ments. No trace of colour remains in the specimens. The body is widest near the 

 anterior end and tapers gradually towards the tail. 



The head (fig. 11 a) is rather elongate, with parallel sides. The dorsal tentacles 

 are at the anterior angles, and the ventral pair are a little further behind on the lower 

 surface of the head. At the posterior dorsal angles of the head are two small rounded 

 papillae. The brain is clearly visible behind the head. It is bilobed, and on its 



