FERTILITY AND HATCHING OF FGGS. 



119 



^'ARIATION IN Fertility and Hatching Oualitv of Eggs. 

 From the figures which are given in Tables II to V inclusive, 

 it is possible to get some exact information regarding the degree 

 and character of variability shov^n by the pullets under dis- 

 cussion in respect to fertility and hatching quality of eggs. 

 The important variation constants for these two characters are 

 given in Table VI. 



TABLE VI. 



Constants of Variation in Fertility and Hatching Quality of 

 Eggs. Calculations from the Data of Tables II-V inclu- 

 sive. 



Chahacter. 



Mean 



Standard deviation. 



(A measure of 



variation.) 



Per cent, of eggs infertile, 1908 j 21.71±0.96 



' " 1909, pullets and year-! 



ling hens combined 14.14±1.1 



Percent, of eg^s infertile, 1909, pullets only 13.65±1.38 



' " " 1909, yearling hens only 15.09±2,01 



' fertile eg^s hatched, 1908 37.24±1.16 



" " " " " " 1909, pullets and 



yearling hens combined 50.68±1 .35 



Percent, of fertile eggs hatched, 1909, pullets only 47. 67 ±1.80 

 " " " " " " 1909,yearling hens 

 oaly 



54.48±1.94 



15.00 + 0.68 



20,56±0.S1 

 19.10±0.9S 

 22.65±1.42 

 ]7.99±0.82 



24.16±0.95 

 24.92±1.27 



21.91±1.37 



From this table the following points are to be noted : 

 I. The mean or average percentage of infertile eggs shown 

 in the breeding records of the 1908 group of birds is approx- 

 imately 22. This is an unduly high percentage of infertility. 

 It is to be explained, however, by the fact, pointed out above, 

 that the breeding work in that year was done under unsuitable 

 housing conditions. In 1909 the average percentage of infer- 

 tility taking all birds of the year together, was approximately 

 14. This reduction of about 8 per cent in the number of infer- 

 tile eggs is directly attributable to the improvement in housing 

 conditions. The figure for 1909 represents a very fair average 

 condition of fertility, taking the whole breeding season through, 

 and remembering that this represents returns on from 5000 

 to 6000 incubated eggs. If the early portion of the breeding 

 season were left out of account the average percentage of infer- 

 tility would be considerably reduced below 14, the figure given. 



