It was observed that a number of loaches (Misgurnus anguillicaudatus) showed an histological abnormality, including a somewhat viscous substance in the uriniferous tubule of the kidney.
Although the temperature of the objects of observation was raised above 39°C, which required 3～5 minutes by hot water at a first cleavage stage of fertilized eggs, the ratio of histological normalities or abnormalities was similar to controles. It is therefore unlikely that the heat shock caused abnormalities. When there was only a small amount of viscous substance in the uriniferous tubules of the kidney, it was deeply stained by Heidenhain's iron haematoxylin, but a large amount was only lightly stained. In the case of a medium amount, the kidney tissue resembled thyroids. The viscous substance was not found in the collected tubules, except in one case.
An abnormality of another type was seen in three instances. It was characterized by several deeply stained dots in the glomeruli. These loaches were reared in 206～218 days and then fixed by a Navaschin fixer, but within that period no individuals died from edema.
The investigated portion being the middle part of the kidney only, it seems that the function of the kidney is sufficiently performed by another, not investigated, part.