EVIDENCE OF GERM CELL SELECTION 399 



C. The control period followed immediately, extending from 

 April 9 to June 12, during which time 166 eggs were laid, eleven 

 of which were lost for purposes of the experiment. The data 

 relative to the remaining 155 are given in table 2. 



Experiment 4. (February 20, 1918, to June 12, 1918). The 

 heterozygous parents were five hens (nos. 21, 22, 23, 24, and 26) 

 from the 1917 chicks, and sisters or half-sisters of males nos. 

 27 and 28. Unfortunately, they were not uniform in type. 

 All were white and all were brachydactyl and booted, but they 

 varied in comb form and in Polydactyly. Nos. 21, 24, and 26 

 were derived from 1-C, nos. 22 and 23 from 1-A. Nos. 23 and 

 24 were poly dactyl, the others were not. The average index 

 of brachydactyly was 91. 



The homozygous parent was an exceptionally fine black 

 Minorca cockerel from the same source as the hens used in 

 experiments 2 and 3. 



Experiment 4 is a reciprocal of experiments 2 and -3. In 

 this case the male produced only one class of germ cells, while 

 the polydactyl females should have produced the eight classes 

 mentioned above and the non-polydactyl hens the classes 

 numbered 3, 4, 7, and 8. Since individual records were not 

 kept, this experiment yields critical data for only brachydactyly 

 and color. 



C For the control, eggs were saved from February 20 to 

 April 24; 151 were laid, of which 150 were incubated (table 2). 



A. Alcohol treatment administered as described in an ear- 

 lier paragraph was begun on April 27. It was planned to give 

 about three hours a day, but this proved to be more than the 

 hens could stand, and individual treatments were frequently 

 cut down to less than an hour. May 5, by an error, only one treat- 

 ment was given and on May 31, the morning treatment having 

 been later than usual, it was not thought safe to risk an after- 

 noon treatment. May 7, no. 24, which had recently laid, died 

 immediately after being removed from the inhalation chamber. 

 May 22, no. 22, died in the chamber, and a few days later no. 

 26 was overcome beyond recovery. Finally, on June 8, no. 

 23, which had been saved with difficulty on two previous 



