1008 Journal of Agricultural Research vol. vi, n . 2S 



dwarf-egg production, both in actual number of dwarf eggs and in the 

 proportion of dwarf to normal eggs produced. It was, however, shown 

 that the maximum dwarf-egg production (either absolute or relative) 

 did not coincide with the maximum normal-egg production. 



Earlier studies (5) have shown a decided relation between the age of 

 the bird and the tendency to produce multiple-yolked eggs — that is, birds 

 are more likely to produce double- or triple-yolked eggs before they are 

 entirely mature than later in life. In this connection it seemed worth 

 while to investigate a possible relation between dwarf-egg production 

 and age. 



There were 189 normal * birds which laid one or more dwarf eggs. 

 These birds laid 205 dwarf eggs. The age of the bird at the time the 

 dwarf egg was laid could be determined in 202 cases. The age frequency 

 distribution is given below. 



Dwarf-egg 

 Age in days. frequency. 



150-209 II 



210-269 14 



270-329 22 



33°-3 8 9 6 5 



390-449 52 



450-509 J 9 



510-569 4 



570-629 o 



630-689 3 



The constants calculated from this frequency distribution are: 

 Mean = 396.53 ±6.43 days; standard deviation = 135.57 ±4.55 days; 

 and coefficient of variation 34.19^: 1.27. These constants must not, how- 

 ever, be accepted as a description of the age variation. It has already 

 been noted that a large proportion of the birds are disposed of at the end of 

 their first laying year — that is, when they are 15 to 17 months of age. 

 There were, therefore, many more chances for a bird to lay a dwarf egg 

 during her first year than later in life. From data in hand it is not pos- 

 sible to decide whether or not a bird is more likely to lay a dwarf egg 

 during the second or third year than during the pullet year. The flocks 

 were not depleted, however, except by the normal small mortality 

 from natural causes, until the end of the first laying year. It may 

 be noted from the distribution that pullets are increasingly likely 

 to lay dwarf eggs up to the time they are 1 year old and that the chances 

 then decrease up to the end of the pullet year. The mean age for dwarf- 

 egg production among pullets may be calculated from the above dis- 

 tribution as far as and including the 450-509-day group. This mean 

 is 361.96 ± 3.75 days, approximately 1 year. It is apparent also that 

 the second year maximum falls in the 690-749-day group — that is, 



1 That is, a complete study of their records, checked in many cases by post-mortem examinations, showed 

 no abnormality. 



Dwarf-egg 

 Age in days. frequency. 



690-749 6 



750-809 2 



810-869 2 



870-929 o 



930-989 o 



990-1,049 1 



1,050-1,109 1 



