Michalowsky in 1925 was the first to produce tumors of the testes in fowls by injecting a 5 per cent solution of zinc chloride. Histological examination of the tumors showed them to be composed of the most diverse tissues, including cartilage, developing bone, glandular formations, cysts, and ducts lined with stratified polymorphous epithelium, smooth and striated muscle, and nerve cells. On account of this variety of tissues the tumors were classified as teratomas. Of particular interest to Michalowsky were certain peculiar cells with a basophilic protoplasm and a clear nucleus, which were scattered throughout the tumor in separate foci or strands. Unfortunately, for a long time these experiments were not duplicated. Thus, some years after Michalowsky9s work had been published, Petrov wrote: “Among the tumors produced by chemical stimulators an isolated place is occupied by the complex teratomas described by Professor Michalowsky. Until his experiments are verified we do not find it possible to pass any judgment upon their significance.” The experiments were repeated in 1936 by an American investigator, Bagg, whose results fully confirmed the data originally obtained. Bagg considered the foci of dark cells, referred to above, as carcinomatous zones, but numerous attempts made to transplant his teratomas were not successful. At the suggestion of Professor Michalowsky experiments on the transplantation of the tumors were undertaken in this laboratory. In March 1937, 19 adult fowls were injected with a 5 per cent solution of zinc chloride, receiving 0.3 c.c. in each testis. Three fowls died soon afterward. In 2 of the 16 survivors teratomas of the testes developed. The first fowl was killed on June 14, 1937, and autopsy revealed a large tuberous tumor arising from the middle of the left testis, weighing 204 gm. and surrounded by a thin capsule through which small cysts were seen. At the site of the injection cyst cavities and small areas of cartilage were observed.