抄録
1. In 1957 a number of the medaka (Oryzias latipes) having vertebral anchylosis resembling the genetic fused (f) were found in a certain region on the outskirts of Nagoya. Characteristics of the “wild fused” and the genetic fused (f) are presented.
2. Breeding experiments performed on the genetic fused (f) confirm Aida's (1930) conclusion that it is a Mendelian recessive and independent from known color genes and the sex.
3. Breeding experiments with the wild fused indicated that the vertebral anchylosis is nonheritable. These anomalies might have arisen from some unusual environmental condition during embryonic life.
4. Artificial induction of nonheritable anchylosis is successfully performed by treating early embryos of normal strain with phenylthiourea.
5. It is pointed out that there are two kinds of vertebral anchylosis in this fish, i. e., hereditary and nonheritable.
