MKTHOD FOR DETERMINING WEIGHT OE PARTS OE EGGS. 97 



A comparison of these tables shows that eggs kept in the 

 open air lose daily from 0.64 gr. to 0.13 gr. with a mean for 

 the first four days of 0.0893, while eggs kept in sealed jars lose 

 daily from 0.00 to 0.04 gr. with a mean for the first four days 

 of 0.0228. That is, keeping the eggs sealed in jars reduces the 

 evaporation to one-fourth that which occurs in the open air. 



In this laboratory egg data are usually taken within 24 and 

 always within 48 hours after the egg is laid. The error due 

 to evaporation which is likely to influence our results is, there- 

 fore, the loss within the first 48 hours. In this time the eggs 

 kept in the open air lost from 0.15 gr. to 0.24 gr. with a mean 

 of 0.199, while those kept in jars lost from 0.02 gr. to 0.06 gr. 

 with a man of 0.042. By keeping the eggs in jars the error 

 due to this cause was reduced to nearly one-fifth that for eggs 

 kept in the open air. The error 0.042 is too small to influence 

 any conclusions likely to be drawn from the data. The method 

 of preserving the egg in sealed jars is, then, sufficiently accurate 

 for the present work. 



Tables I and II show further that there are individual dif- 

 ferences in the amount of weight lost by eggs kept under iden- 

 tical conditions. For eggs kept in the open air the minimum 

 mean daily loss for the first four days was 0.07 (egg no. 40) 

 and the maximum was 0.115 (egg no. 38). On the sixth day 

 these two eggs still represent the extremes* with mean daily 

 losses of 0.0667 ^^^ 0.1067 respectively. For the -eggs kept in 

 sealed jars the minimum mean loss per day for four days was 

 0.0125 (egg no. 28) and the maximum was 0.03 (egg no. 29). 



These individual differences are no doubt due largely to vari- 

 ation in the character of the shell in the eggs of different indi- 

 vidual birds. The fact that — especially in the eggs exposed to 

 the open air — the loss of weight in heavy eggs is greater than 

 that in light eggs indicates that the amount of exposed surface 

 and consequently the size of the egg is another factor. The 

 relation between size of eggs and loss of weight is shown 

 graphically in Fig. yT,- 



*Egg no. 36 also has a mean daily loss of weight of 0.0667 for six 

 days. 



