414 RUTH J. STOCKING 



If hereditary variations are frequently occurring, aside from 

 Mendelian recombinations, it should be possible to find them in 

 vegetative reproduction. Here we are freed from the mixing 

 of types which makes these relations so difficult to interpret in 

 biparental reproduction. The hereditary abnormalities with 

 which the present study deals seem to offer a favorable oppor- 

 tunity for the study of this matter. Within the same line of 

 vegetative descent we find individuals that are in appearance 

 normal, others that are outwardly abnormal. Can we by con- 

 tinued selection of normal individuals on the one hand, of abnor- 

 mal individuals on the other, break our single stock into two or 

 more, differing in hereditary constitution? 



Experiments in selection 



To answer the question just proposed, selection was carried 

 on for many generations in a considerable number of abnormal 

 stocks. 



As before set forth, some of the races in which abnormalities 

 occurred gradually changed character and became entirely nor- 

 mal. In other races both normals and abnormals appeared for 

 long periods, giving opportunity for long continued selection. 

 We will first take up the large race C, of Experiment 1. 



Figures 10 and 11 give extracts from the pedigree of race C. 

 This race, derived from exconjugant 101a, of Experiment 1, was 

 kept for 191 days and produced during that time 4710 indi- 

 viduals in the observed cultures; 2683 of these were abnormals. 

 The early history of this race is shown in chart 1. 



Chart 1 

 Early history of Race C 

 (rt = normal; ab = abnormal) 

 December 2 5 7 9 11 13 15 17 



fSn — 1 4n — 1 Discontinued 

 In— 1 4n— 4 8n— 2 8n— 1 4n— 1 j lab— 1 lab— 1 Dead 



Lln.b— 1 lab— 1 Race C 



In this and in the succeeding charts the first figure under each date shows the 

 number of animals present in that line on that date; n means that these were nor- 

 mal; ab means that they were abnormal. The second figure, following the dash, 

 denotes the number chosen to carry on the slide line, the others being put into 



