IOI2 



Journal of Agricultural Research 



Vol. VI, No. 25 



Table XXV. — Mean standard deviation, j3 lt /3 2 , and the difference between the similar 

 constants for the two distributions for the actual frequency distribution of the position 

 of dwarf eggs in the litter and for an ideal evenly distributed frequency of the same size a 



"These constants are equal for any evenly distributed 10-class frequency with a class unit of 0.1, but 

 the probable errors given in the table are calculated on the basis of 183 observations. 



The last line of Table XXV shows that in no case does an essential 

 constant for the actual curve differ from the similar constant for the 

 ideal curve by an amount which is certainly significant — that is, the 

 irregular fluctuations of the frequency curve for the litter position of 

 dwarf eggs are not greater than the expected fluctuations of a random 

 sample of the same size drawn from a population evenly distributed 

 over the range. The present data, then, indicate that a dwarf egg is 

 equally likely to occur at any time during a period of production. 



C. — POSITION IN THE CLUTCH 



A fowl seldom lays on every day during a litter. The actual time 

 between successive eggs depends on the rate of fecundity of the indi- 

 vidual at the time. This rate differs greatly with the individual and 

 with the season of the year. It also, in general, increases from the 

 beginning of a litter to a maximum and then decreases toward the end 

 of the period of reproduction (4, 19). Since fecundity finds its mani- 

 festation in discrete units (eggs) , the result of a very low rate is expressed 

 by the production of an egg on a day preceded and followed by one to 

 several days on which no egg is produced. A common low fecundity 

 rhythm results in the production of an egg on every second day. More 

 usually an egg is produced somewhat later on each of two or more suc- 

 cessive days, and then a day follows on which no egg is produced. The 

 next egg is produced early on the following day. The litter is thus 

 objectively broken into a series of daily eggs, which we may call 

 "clutches," separated by one or more days on which no egg is produced. 

 The size of a clutch varies from one egg to the extreme and unusual 

 cases where a whole litter (sometimes of more than 40 eggs) is laid in a 

 continuous daily series. 



The general acceptance of the notion that a dwarf egg marks the end 

 of a period of production suggests an investigation of the position of the 

 dwarf egg within its clutch. In 197 of the cases where a normal bird 

 produced a dwarf egg the bird completed the clutch to which the dwarf 



