GENETIC STUDIES IN POULTRY. 229 







Of the 2,266 individuals shown in the above table 8.12 per cent, 

 were embryos dead between the twelfth and eighteenth days of 

 incubation, 22.11 per cent, between the eighteenth and twenty- 

 first days, and 69.77 per cent, were chicks sexed after hatching. 

 It is interesting to note in this connection that the most critical 

 period of development is apparently between the eighteenth and 

 twenty-first days of incubation. Of all eggs set and dying in the 

 embryonic stage, 361 or 34.5 per cent, died before the twelfth 

 day of incubation, 184 or 17.6 per cent, between the twelfth 

 and eighteenth days, and 501 or 47.9 per cent, during the last 

 three days of incubation. 



The sex ratio is listed each week for the three classes Ds, DS 

 and chicks hatched respectively, together with the totals for 

 each week and the total ratio of each class for the entire period 

 with the corresponding ratio of males. These data in Table II. 

 represent a total of 79.20 per cent, of all fertile eggs set during 

 this time. Of the remaining 20.8 per cent, upon which the sex 

 was not determined 12.62 per cent, or 361 died before the twelfth 

 day of incubation and 8.18 per cent, or 234 were lost due to the 

 causes listed. 



In the DZ class with the exception of the last two weeks in- 

 terval the sex ratio is comparatively high, ranging from 52.83 to 

 64.70. However, no general trend is apparent during the con- 

 secutive intervals as the highest sex ratio appears in the interval 

 from March 4 to 1 1 and the next highest in the period of April 

 15 to 22. 



Of those embryos dying between the eighteenth and twenty- 

 first days of incubation no general trend of the sex ratio is like- 

 wise apparent. In general, however, the sex ratio is lower than 

 among the D& class. 



Of the chicks sexed after hatching no particular trend is noted 

 in the sex ratio from the beginning to the end of the hatching 

 season. The per cent, of males of the chicks hatching varies 

 from 46.37 to 54.00 with an average of 50.85. From the total of 

 2,266 chicks and embryos examined 1,170 or 51.63 per cent, are 

 males and 1,096 or 48.37 per cent, females. 



Some of the data included in Table I. were not complete for 

 the whole season. These were obtained in both 1924 and 1925 



