Volume 33, Issue 6
June 1951, pages 297-330
pp 297-321 June 1951
The comparative histology of the alimentary canal ofRita rita Ham.,Ophicephalus gachua Ham., andCirrhina mrigala Ham., has been studied , to correlate the histological structure with the nature of food.
In addition to the ordinary epithelial cells, the epidermis of the skin contains mucus-cells and club-cels inRita rita; sac-cells inOphicephalus gachua; and only club-cells inCirrhina mrigala. Taste-buds are present only in the skin ofRita rita. InCirrhina mrigala the club-cells have been seen being extruded bodily from the epidermis, thus providing a strong evidence for the view that the club-cells have an excretory function.
The histological structure of the buccal cavity and the pharynx is the same as that of the integument. Taste-buds and mucus-cells are present in the buccal cavity and pharynx ofCirrhina mrigala. InOphicephalus gachua a few taste-buds are present on the tongue but none in the buccal and pharyngeal epithelia.
In the œsophagus the epithelium is simple. No club-cells are present inRita rita andCirrhina mrigala, but inOphicephalus gachua sac-cells are profusely abundant.In Cirrhina mrigala a few taste-buds extend even upto the œsophagus. This has been correlated with the food of this fish.
A true stomach is present in the two carnivorous fishesRita rita andOphicephalus gachua, but in the herbivorous fishCirrhina mrigala it is absent as shown by (i) the absence of gastric glands, (ii) opening of bile-duct just behind the œsophagus, and (iii) the part following the œsophagus having the typical structure of intestine. The absence of a stomach inCirrhina mrigala has been correlated with its food. The cells forming the gastric epithelium inRita rita andOphicephalus gachua are mucoid in nature. Oxyntic cells are absent.
InCirrhina mrigala the intestine is exceedingly long and coiled but in the other two fishes it is short and straight. This difference has been correlated with the difference in food in these fishes. InCirrhina mrigala the first part of the intestine is dilated and is called the ‘intestinal bulb’. In the region just behind the intestinal bulb the mucous membrane is transversely folded. In the rest of the intestine, as also in the intestinal bulb, the mucosa is longitudinally folded. No multicellular glands are present in the epithelium of the intestine. The mucus-cells (goblet-cells) are present in the intestine of all the three fishes studied. The mucus-cells make their appearance for the first time in the intestine inOphicephalus gachua.
Pyloric cæca, present only inOphicephalus gachua amongst the fishes studied, have the same histological structure as the intestine.
The rectum differs from the intestine only in having thicker muscular coats and more numerous mucus-cells,
pp 322-326 June 1951
Both molasses andmohua flowers serve as source of energy for azotobacter, but the amount of nitrogen fixed per gram of material or per gram of carbon supplied is much less than in the case of mannite. In this respect,mohua flowers which contain larger amount of nitrogen than molasses are a greater offender. Even at very low concentrations, molasses is less efficient than mannite.
pp 327-330 June 1951
It is suggested that the unilocular ovary of the Compositæ may have originated as a result of the gradual suppression or incomplete development of the septum separating the two locules in the ovary of the Stylidiaceæ. It is also possible that the unilocular condition of the Compositæ may have been derived as a result of abortion of one of the locules, for, this tendency is already evident in certain species ofStylidium likeS. adnatum.