A year ago after centrifuging some eggs of Rana sylvatica it was noted that all of the survivors in one lot had accessory tail-like appendages. This seemed to be a sufficiently striking modification to merit some effort to learn just what was responsible for their occurrence. After many trials similar modifications were produced again this season. Eggs were treated in various stages from unsegmented eggs to the gastrula, and the different lots were given three different treatments. In this note the earlier stages will not be considered. In a stage at which the blastopore had just become evident, or soon afterward became evident, the eggs which were subjected to a centrifugal force equivalent to 1,700 times gravity for two minutes were mostly killed. Accessory tail-like appendages developed in the survivors. 1,350 times gravity killed very few and accessory tail-like appendages developed in all of the survivors. 200 times gravity for ten minutes produced all normals in cases where the blastopore was not yet evident at the time of treatment. Where the blastopore was just evident all produced the accessory appendages. All survivors of similar treatments in the advanced gastrula and later stages were normal and accessory appendages were not produced in earlier stages than the blastula. The accessory appendages, usually one to each animal although in some instances as many as four have been noted, occurred on different parts of the body. By far the commonest location was the mid-ventral region although they were in all positions from the anal region to the under side of the head. In many cases the position was more or less lateral, or even dorso-lateral, the appendage usually extending ventrally however. The appendages in the positions described were all distinctly tail-like having the characteristic myomeres seen in the normal tail and having a fin-likekeel on one or both margins.