THE PRODUCTION OF ACCESSORY APPENDAGES AND ANTERIOR DOUBLING IN FROG EMBRYOS BY CENTRIFUGAL FORCE

Abstract

In looking through the literature one finds that very little work has been done on the effect of centrifugal force on the blastula of the frog or salamander. We feel that this technique may be applied with advantage to problems of amphibian experimental embryology. This belief is supported by the inter- esting results obtained by Banta and Gortner ('15) in cen- trifuging the eggs of Ran a sylvatica. These authors found that headless monsters and tadpoles with accessory appendages were produced when eggs in the early blastopore stage were centrifuged at speeds varying from 200 times gravity to 1200 times gravity. It was in an attempt to confirm the work of Banta and Gortner and to discover whether other types of abnormalities could be produced in the frog egg by centrifugal force, that the experiments reported here were carried out. The eggs which were used in the present experiments were of Rana sylvatica, and were collected in the vicinity of Gambier, Ohio, during the months of March and April, 1938. Five clusters of eggs were used, each cluster containing from 150-200 eggs. Two thirds of the eggs in each cluster were centrifuged at speeds indicated below, the remaining one third of the eggs in each cluster served as controls. The first series (cluster 1), was composed of eggs in the mid-gastrula stage and these eggs were centrifuged at 1400 r.p.m. for ten minutes. The second series (cluster 2) was composed of eggs in the late blastula stage and these were centrifuged at 1400 r.p.m. for ten minutes. The third series (cluster 3) was composed of eggs in the early blasto- pore stage and these were centrifuged at 1800 r.p.m. for five minutes. The fourth series (cluster 4) consisted of eggs likewise in the early blastopore stage. These were centrifuged at 2900 r.p.m. for ten minutes. Eggs in the fifth series (cluster 5) were in the late blastula stage and these also were centrifuged at 2900 r.p.m. for ten minutes. The eggs in series I, which were in the mid-gastrula stage at the time of centrifuging, developed normally. A large per-