Studies on the morphology and histology of the digestive tract of Bagarius bagarius (Ham).

1. The alimentary tract of Bagarius bagarius is long in accordance with its omnivorous nature and consists of buccal cavity, pharynx, oesophogus, stomach, intestine, and rectum. 2. The month is terminal and bounded by upper and lower lips, which are provided with many villiform teeth. 3. The buccal cavity and pharynx are dorso-ventrally flattened with smooth lining in the former and folded in the latter. Taste buds and mucous cells are present in these parts which help in selection of food and inlubricating the prey respectively. 4. The oesophagus is small but wide and produced into longitudinal folds. Histologically it is composed of the usual 4 layers viz. serosa, muscularis, submucosa and mucosa. The mucosa is stratified and bears mucous cells. 5. The stomach is large, sac-like and divided into a large cardiac and a small pyloric portion. In the submucosa of the cardiac part, gastric glands are present into the cryps of mucosa. 6. The intestine is distinguished into duodenum, ileum and rectum on the basis of folds. These folds are of honey comb type in duodenum, longitudinal in the ileum, and anatamosing in the rectum to form a honey comb. The muscularis of the duodenum is better developed than that of the ileum and is best formed in the rectum, where the mucosa contains abundant mucous cells. 7. The liver consists of 2 lobes and is formed of polygonal cells. Blood capillaries and hepatic ductules are present in it. The gall bladder lies in between the right lobe of liver and duodenum. It consists of connective tissues lined with columnar cells on inner side and serosa on the outer side. 8. The pancreas is diffused and lies concentrated between the liver, stomach and the coils of intestine. It is composed of polyhedral cells, which are aggregated to form acini. The pancreatic tissue is supplied with the pancreatic ductules and blood capillaries.

Studies on the extent of gill surface in a fresh water cat-fish Bagarius bagarius (Ham.).

The total gill area of the fish ranges from 37,537 to 56,551 lamellae. The number of lamellae per mm of the gill filament and area of lamellae knowing the respiratory gill area, the gill area per g of body weight and per cm3 of body volume were calculated to correlate the variation in gill surface area per unit weight and volume of the fish. The fish can survive for quite long out of water as the lamallae are spaced wide apart and do not adhere together.