1. ^*Department of Biology
2. ^†Department of Pathology, Faculty of Medicine, Zagreb, Yugoslavia.

Abstract

WHEN Stevens transplanted mouse ova at the one and two cell stage into the testis of a 129/Sv mouse, teratomas consisting of several types of differentiated and undifferentiated tissues resulted¹. Tumours developed only when transplantation was into the 129/Sv-Sl^JCP strain, known for developing frequent spontaneous testicular teratomas. In other strains of mice, Stevens¹ obtained no growth of tubal ova after transplantation into the testis. Kirby² obtained only trophoblast and extraembryonic derivates after grafting tubal eggs under the kidney capsule and in the testis, but when he grafted blastocysts the egg-cylinder developed. Similar results were reported^3–6, but the experimental period was too short (up to 15 days) for histogenesis. Nicholas⁷ reported histogenesis after the transfer of tubal eggs under the kidney capsule, but his experiments have never been repeated successfully. Histogenesis and full differentiation are probably stopped by trophoblastic overgrowth^5,6. Grobstein⁸ and Levak-vajger and N. S.⁹ found fully differentiated adult tissues in rat egg-cylinder grafts maintained for 30 days in the anterior chamber of the eye. They found no evidence of atypical or malignant cells.