iooo Journal of Agricultural Research Vol. vi, No. as 



4. The correlation between yolk weight and egg weight in dwarf eggs 

 with small yolks is very high. Since the yolk weight forms part of the 

 egg weight, we will confine our discussion to the correlation between yolk 

 weight and albumen weight. This correlation is also very high. It is 

 in fact higher than the average correlation between yolk weight and 

 albumen weight within the normal eggs of a single individual. This high 

 correlation between yolk weight and albumen weight in dwarf eggs with 

 small yolks adds to the evidence already presented that the amount of 

 yolk present in the duct is an important factor in determining the amount 

 of albumen secreted, and thus both directly and indirectly influences the 

 size of the egg. 



V.— FREQUENCY OF THE OCCURRENCE OF DWARF EGGS COMPARED 

 TO NORMAL EGGS AND OF DWARF EGG PRODUCERS COMPARED 

 TO BIRDS WHICH DO NOT LAY DWARF EGGS. 



As previously stated, the period covered by this investigation extends 

 from February 1, 1908, to February 1, 191 6. During this period it has 

 been the practice to make up the flock in September or early October. 

 A few of the birds of the previous flock are saved for specific experiments 

 and the rest killed or sold. The pullets are put in the houses at this time. 

 The 298 dwarf eggs collected were thus produced by nine different flocks 

 of birds. The number laid by each flock is given below: 



Number 

 of dwarf 



eggs. 



Feb. 1, 1908, to Aug. 31, 1908 16 



Sept. 1, 1908, to Aug. 31, 1909 20 



Sept. 1, 1909, to Aug. 31, 1910 34 



Sept. 1, 1910, to Aug. 31, 1911 43 



Sept. 1, 1911, to Aug. 31, 1912 59 



Sept. 1, 1912, to Aug. 31, 1913 17 



Sept. 1, 1913, to Aug. 31, 1914 27 



Sept. i, 1914, to Aug. 31, 1915 72 



Sept. 1, 1915, to Feb. 1, 1916 10 



Feb. 1, 1908, to Feb. 1, 1916 298 



The first and last years are, of course, incomplete. The fluctuations be- 

 tween the other years are no doubt due largely to three causes. First, the 

 size of the flock differs somewhat from year to year. Second, the average 

 annual egg production fluctuates with changes in the proportion of low 

 and high laying strains which compose the successive flocks — for example, 

 the 1914-15 flock contained 55 less birds than the 1911-12 flock, and at 

 the same time produced 25,374 more eggs, so that although it produced 22 

 per cent more dwarf eggs, the proportion of these eggs to the normal eggs 

 was smaller. Third, as will be discussed later, certain birds suffer dis- 

 turbances of physiology which cause them to produce a number of dwarf 

 eggs. Such birds do not occur every year ; in fact, an unusual proportion 

 of the known cases occurred during the two years of highest dwarf-egg pro- 



