THE KIDNEY OF LIPOTES VEXILLIFER

Kidneys of four male and nine female Lipotes were examined. The kidneys increase in length and weight as the dolphins grow up. Their structure is as a rule similar to that of other cetaceans, but some additional features are present in Lipotes. In com parisons with the kidneys of other freshwater dolphins, the number of reniculi in Lipotes is greater than that in Platanista gangetica, fewer than that in Inia geoffrensis and closer to that in Pontoporia blainvittei. The indices of the kidney and the reniculi in young Lipotes axe similar to those in Platanista gangetica and Inia geaffrensis, but much higher in adult Lipotes than those in other freshwater dolphins. According to our materials studied, the reniculus clusters in the kidney of the Lipotes have been present even at the stage of newborn and the degree of the renicularisation increases with the growth of the animal. Hence it is inadequate to regard this structure as a secondarily-evolved phenomenon. Moreover, we found that the arrangement of the sporta perimedullaris musculosa in reniculus of Lipotes is irregular.