By excising a 3-day-old interfrontal suture with adnexa and transplanting it into the sagittal suture of a 10-week-old rat of the same inbred strain, the development of the interfrontal suture under experimental conditions could be studied. The effect was a distinct delay of the moment of closure of the suture, namely, from normal period of 1 week to that of 4 or 5 weeks. It was found that after an initial osteosynthesis, the interfrontal suture reopened and then became part of the system of open sutures in the cranial vault of the donor rat.