1. African native cichlid T. mossabica showing 100% survival in the sea water of 75% concentration and a lesser survival in undiluted sea water without acclimation procedure was proved to better excel in salinity tolerance than T. nilotica and T. sparrmani (Fig. 1).
2. The kidney of Tilapia exhibits the structure of typical freshwater fish. The scanty interstitial connetive tissue of kidney is characteristic of the fishes Genus Tilapia.
3. A pomacentrid Abudefduf vaigiensis which is provided with the kidney of typical marine fish (lacking in the distal convoluted segment), shows the approximate half value of the size in each component of the kidney. A South American cichlid Pterophyllum eimekei exhibiting freshwater fish type in terms of kidney-structure is the intermediate values between Tilapia and A. vaigiensis (Table 1 and Fig. 2).