Seasonal histological changes in the gonads of two teleost fishes, Notopterus notopterus (Pallas) and Colisa fasciatus (Bloch. Schn.).

1. The reproductive cycle of the gonads of the Notopterus notopterus and Colisa fasciatus have been studied in the present account. 2. In the ovary of both the fishes same developmental stages have been observed. Ovarian cycle is distinguished in the 4 phases depending upon their changes in nucleus. Before spawning the enlargement of the ovary is due to the accumulation of the yolk in the egg. 3. Similar accounts of 4 important stages in the maturation of testis are given. A detailed description is given to gametogenesis in both species, and correspond closely with the macroscopic field stages. The tubules of testis in both the fishes are divided by the connective tissue strands. Spermatogonia present in these tubules play main part in spermatogenesis. 4. The spawning in both the fishes occurs during late May to August.