Accessory Appendages in Amphibian Larvae. 177 



108 (925) 



The production of accessory appendages and other abnormalities 

 in amphibian larva? through the action of centrifugal force. 



By Arthur M. Banta and Ross Aiken Gortner. 



[From the Station for Experimental Evolution, The Carnegie Insti- 

 tution of Washington.] 



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 un- 

 segmented 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 minute s 

 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 appen- 

 dage usually extending ventrally however. The appendages in the 

 positions described were all distinctly tail-like having the charac- 

 teristic myomeres seen in the normal tail and having a fin-like 



