Orissa may be described in general terms as consisting of the coastal area of Bengal south of the Gangetic delta. It extends in inland, however, for a considerable distance and includes hilly tracts. There is no geographical boundary between it and the north-eastern part of the Madras Presidency or the eastern part of the Central Provinces.
Chilka Lake.—This marine lake is a shallow lagoon measuring about 40 miles in length and 10 miles in breadth, and formed in geologically recent times by the growth of a narrow sand-bank across the mouth of a wide bay. At its northern end it communicates with the sea by a narrow channel, and throughout its length it is strongly affected by the tides. At its south end, which is actually situated in the Ganjam district of Madras, the water is distinctly brackish and is said to be nearly fresh at certain times of year. At this end there are numerous small artificial pools of brackish water somewhat resembling those of Port Canning as regards their fauna.
Sur (or Sar) Lake.—A shallow, freshwater lake of very variable size situated a few miles north of Puri on the Orissa coast. In origin it probably resembled the Chilka Lake, but it is now separated from the sea by about 3 miles of barren sand dunes, among which numerous little pools of rain-water are formed during the rains. These dry up completely in winter, and even the lake itself is said sometimes almost to disappear, although when it is full it is several miles in length. The fauna is essentially a freshwater one, but includes certain Mysidæ and other crustacea usually found in brackish water.
Bombay Presidency.
Bombay.—The town of Bombay, built on an island near the mainland, is situated close to swamps and creeks of brackish water not unlike those that surround Calcutta. Its "tanks," however, differ from those of Calcutta in having rocky bottoms and, in many cases, in drying up completely in the hot weather. Of the fauna of the swamps extremely little is known, but so far as the sponges and polyzoa of the tanks are concerned the work undertaken by Carter was probably exhaustive.
Igatpuri.—Igatpuri is situated at an altitude of about 2000 feet, 60 miles north-east of Bombay. Above the town there is a lake of several square miles in area whence the water-supply of several stations in the neighbourhood is obtained. The water is therefore kept free from contamination. The bottom is composed of small stones and slopes gradually up at the edges. During the dry weather its level sinks considerably. Several interesting sponges and polyzoa have been found in this lake, most of them also occurring in a small pond in the neighbourhood in which clothes are washed and the water is often full of soap-suds.
Southern India.
Madras.—The city of Madras is built by the sea, straggling over a large area of the sandy soil characteristic of the greater part of the east coast of India. In wet weather this soil retains many temporary pools of rain-water, and there are numerous permanent tanks of no great size in the neighbourhood of the town. The so-called Cooum River, which flows through the town, is little more than a tidal creek, resembling the Mutlah River of Lower Bengal on a much smaller scale. The sponges and polyzoa as yet found in the environs of Madras are identical with those found in the environs of Calcutta.
Bangalore.—Bangalore (Mysore State) is situated near the centre of the Madras Presidency on a plateau about 3000 feet above sea-level. The surrounding country is formed of laterite rock which decomposes readily and forms a fine reddish silt in the tanks. These tanks are numerous, often of large size, and as a rule at least partly of artificial origin. Their water supports few phanerogamic plants and is, as my friend Dr. Morris Travers informs me, remarkably free from salts in solution. The sponge fauna of the neighbourhood of Bangalore appears to be intermediate between that of Madras and that of Travancore.
The Backwaters of Cochin and Travancore.—The "backwaters" of Cochin and Travancore were originally a series of shallow lagoons stretching along the coast of the southern part of the west coast of India for a distance of considerably over a hundred miles. They have now been joined together by means of canals and tunnels to form a tidal waterway, which communicates at many points directly with the sea. The salinity of the water differs greatly at different places and in different seasons, and at some places there is an arrangement to keep out sea-water while the rice-fields are being irrigated. The fauna is mainly marine, but in the less saline parts of the canals and lakes many freshwater species are found.