1921.] Fauna of the Chilka Lake : Polychaeta. 571 



There remain four species not included in the above groups. Glycinde oligodon 

 was found at eleven stations in the southern end of the lake, and at one station in the 

 inner part of the Channel, south of Mahosa, so that it may be considered as essentially 

 belonging to Group I. Heteromastus similis was taken at three stations between 

 Nalbano and Barhampur, that is to say, near the inner entrance to the lake. It is 

 thus intermediate in distribution between the two groups, and probably likes the 

 bottom of muddy sand which occurs there. Diopatra variabilis was found at eight 

 station in the south end of the lake, twice near the middle, and once at the north- 

 west corner, off Kalapara Ghat, so that it probably belongs to Group I. Ancistrosyllis 

 constricta was taken four times at the south end of the lake, and twice in the Outer 

 Channel during the freshwater season, though it probably lives there the whole year 

 round. Of all the Polychaetes in the lake, this is the species which can endure the 

 greatest range of conditions. A more complete knowledge of the distribution of the 

 species in the lake might cause some changes in this grouping, though probably not 

 to a great extent. The species in Group II have to endure much greater variations 

 in the salinity of the water than those in Group I. It would, however, be rash to 

 claim that the salinity is the determining factor. The species found in the Outer 

 Channel are sand-loving forms, whilst those in the lake are chiefly mud-loving, 

 though some of them live in sponges, etc. The faunistic boundaries are probably two 

 in number, one lying close to the inner entrance of the lake near Barhampur, and 

 limiting the inward range of the sand-loving euryhaline species of the Outer Channel ; 

 the other lying in the area roughly bounded by Patsahanipur — Nalbano — Parikudh 

 — -Kalidai Id. — Barkul Point, and cutting off, in the south end of the lake, the mud- 

 loving species living in water of low, but not greatly varying salinity. There is not 

 yet sufficient evidence to decide whether the determining factor is the salinity of the 

 water or the nature of the bottom. 



Annandale (1915, p. 7) has stated, with reference to the Chilka Lake fauna, that 

 "the great majority of what we may call the permanent residents are, for the reasons 

 that I have already given you, very ordinary in appearance. There is an absence 

 both of brilliant colours and of colouration specially in a high degree adapted for 

 concealment. There is a lack of bizarre form, and the majority of the animals are 

 not modified structurally to a visible extent." Our complete ignorance of the littoral 

 Polychaeta of the Bay of Bengal prevents any analogous statements being made here. 

 To anyone accustomed to examining the Polychaeta of the European coasts, a collec- 

 tion which, out of 17 genera, contains representatives of Ancistrosyllis, Tylonereis, 

 Glycinde, Myriochele, Heteromastus, Sternaspis, Laonome, and M anayunkia, cannot be 

 considered as ordinary in appearance. This impression is also greatly strengthened 

 if the species from the Gangetic Delta are added, though it might be dissipated by a 

 knowledge of the species in the adjacent sea. 



It may be stated generally that the species in Group I are adapted for life in waters 

 of low, but not very variable salinity, and the majority of them prefer a muddy bot- 

 tom. The species in Group II can live in water ranging in salinity from quite fresh to 

 normal sea-water of the Bay of Bengal, and they seem to prefer a sandy bottom. 



