No. 577] UNIT-CHARACTER CONSTANCY 



25 



of modification. These selection experiments are still in 

 progress, but will be reported upon at another time. 



The single-gamete experiment, with which this report 

 will deal, was placed in the hands of the junior author, 

 who has carried it out at the Rhode Island Agricultural 

 Experiment Station. 



As foundation stock for the experiment a single hetero- 

 zygous English rabbit of standard character (grade 2, 

 Fig. 5) was selected. To mate with him, it was desired 

 to obtain a distinct breed of rabbits, free from the Eng- 

 lish pattern, and as pure (uniform) in all respects as 

 possible. For this purpose the "Belgian hare" was 

 chosen. A buck and two does obtained from Mr. G. W. 

 Felton, Cliftondale, Mass., were found to breed very true. 

 From them was bred a stock of does very uniform in 

 character, twelve of which, together with one of the par- 

 ents (2A), were mated with the selected English buck 

 which we may henceforth call by his record number 

 The young thus produced will be called "Series I" off- 

 spring. About half of them were self (non-English), the 

 remainder (187 in number) were English. 2 The latter, 

 although all undoubtedly heterozygous, varied in white- 

 ness from grade 1 to grade 4 (Figs. 1-4), the modal or 

 commonest condition being about the same as that of the 

 father (grade 2). The distribution of the young in rela- 

 tion to our grades is shown in Table I. Statistical treat- 

 ment of the table gives the average grade of the young as 

 2.43, that is somewhat darker than the father. Inspec- 

 tion of the table shows that more than half of the young 

 are darker than the father, which supports in a general 

 way the statistical average grade. If we consider sepa- 

 rately the average grade of the young produced by each 



2 The total number of young obtained from J21A, when mated with Bel- 

 gian hare does, has been to the time of writing 436. The English young 

 now number 210, the non-English (self) number 226. For Series II mat- 

 English, 219, non-English 190, total 415. For Series I and II combined 

 the numbers are: English 429, non -English 422, total 851. This is un- 

 mistakably a 1: 1 Mendelian ratio. 



