Abstract
1. One-half of an anterior pituitary obtained from a young male mouse was transplanted into newborn mice of both sexes. Mice were killed at 100days of age. 2. Female mice bearing the pituitary isografts showed irregular reproductive cycles i.e., prolonged estrus and/or prolonged diestrus. After ovariectomy, such animals exhibited persistent diestrus. 3. The mean pituitary weight in female and male mice bearing the isografts was low than that in the controls. 4. In mice bearing the isografts, ovaries contained large follicles and corpora lutea, and testes were producing spermatozoa. 5. Adrenals of all mice bearing pituitary isografts showed juxtamedullary brown degeneration; this was not seen in controls. 6. The mammary glands in adult mice showing prolonged diestrus after the neonatal implantation of the pituitary glands possessed well-developed duct branching and some alveoli.
