The present paper describes the results of a study on the salinity tolerance of two freshwater fishes, Gambusia aftinis (Baird & Girard) and Heteropneustes fossilis (Bloch). The two species were treated with various concentrations of sea water and three most common salts found in the saline waters of Iraq, namely sodium chloride, calcium chloride and potassium chloride. The mortality rates following these treatments were recorded. Both species showed the highest degree of resistance for sea water and sodium chloride, and the lowest degree of tolerance to potassium chloride. Gainbrtsia afinis was more resistant to these salts and sea water than IT. fossilis.

The testes of Barbus luteus are a pair of elongated structures composed of an anastomosing system of seminiferous lobules. Six spermatogenetic stages of germ cells have been described in the gonad. The endocrine factor lies in the interstitial cells. Spermiation occurs during the months of May, June and July. Fertilization appears to be external. Un‐expelled spermatozoa undergo pycnotic degeneration. The testes show a regular annual cycle which has been described in five arbitrary stages.

The present paper describes the morphology, histology, and annual cyclical changes in the ovaries of Burbus luteus (Heckel). The ovaries are paired structures, joined by short oviducts. The ovarian structure consists of a number of lamellae, which contain the germ cells in various phases of maturation-immature, maturing and mature. Two types of yolk have been reported in the oocyte. The endocrine function of the gonads has been attributed to the follicular cells forming the ' pre-ovulatory corpus luteum ' and ' postovulatory corpus luteum '. The ovaries undergo a regular annual cycle which has been divided into five stages, based on various criteria, vlz, ovarian size, colour, gonosomatic index, average ova-diameter, histological composition, and the spawning activity.

The food habits of the mudskipper, Pseudapocryptrs dentatus (Val.) ranging from 43 to 205 mm in total length collected from the mudflats at Fao estuary, Iraq were studied. A combination of numerical, frequency occurrence and gravimetric methods was used to analysc the stomach contents, both qualitatively and quantitatively. The fish was found to be a strict herbivore and a frequent feeder. It fed solely on phytoplankton dominated by benthic forms. Diatoms were the most important food item in respect ofboth numerical and frequency occurrence methods comprising about 84% of the total number of phytoplankton organisms. The types of phytoplankton that contributed significantly to the diet were, in decreasing order of importance, Pleurosigma, Navicuh, Nitzschia, Synrdra, Closteriopsis and Oscillatoria. Larger fish had consumed lesser amount of food, and there was usually a gradual decrease in consumption with increase in size. The mudskipper consumed food ranging from 1-3 to 105% ofits body weight.

A study on the diurnal feeding cycle of the catfish, Heteropneustes fossilis (Bloch) from the Ashar Canal, Shatt-al-Arab at Basrah was carried out. The stomachs of the fish contained food almost throughout the 24-hour period. Botb average index of fullness of the stomachs and the average points showed two peaks in the feeding cycle of the fish-•one at 0500 h and the other at 1700 h. Thirty-three kinds of food organisms were found in the stomachs of the fish. Aquatic plants formed the major bulk of the diet. The next important foods were entomostracans, aquatic insects, fish parts, molluscs and nonaquatic organisms.The feeding chronology of freshwater fishes has received considerable attention during recent times (Childers and Shoemaker