A nephroblastoma in a fire-bellied newt, Cynops pyrrhogaster.

Nephroblastomas seem to be very rare in animals with mesonephritic kidneys (fishes and amphibia), although immense numbers of many species are kept as pets and in laboratories. A single case was recorded in the steelhead trout (5). The steelhead trout (Salmo gairdneri, Rich.) is the same species as the rainbow trout, differing only in that it spends part of its life in the sea and returns to fresh water to spawn. Twelve nephroblastomas were discovered among 100 rain bow trout during experiments on the hepatocarcinogenic properties of Af-nitrosodimethylamine (1). Still another nephroblastoma in a rainbow trout was identi fied by the late C. E. Dunbar, who contributed sections of his specimen (RTLA Accession No. 217) to the Registry of Tumors in Lower Animals of the Smithsonian Institution. More recently, a nephroblastoma in a marine fish, the striped bass (Roccus saxatilis), was discovered and submitted to the above Registry by Dr. C. F. Helmboldt (RTLA Accession No. 292). Information regarding the latter 2 specimens was kindly provided by Dr. John C. Harshbarger, Director of the Smithsonian Registry (4). In Anurae (Amphibia) of which the South African clawfooted toad Xenopus iaevis is especially widely used in laboratories, only one case of this tumor has been recorded in a fully grown female (3). In the second order of the amphibia, the urodeles, to which the salamanders belong, no nephroblastomas have been described.