Sept. 18. 1916 



Dwarf Eggs 



1015 



would be expected from errors in sampling. The mean and the three 

 constants which define frequency curves, standard deviation, /3 t and 

 /S 2 , were calculated for the actual and the ideal distribution. It has 

 already been pointed out that two distributions with the same num- 

 ber of observations which differ significantly will show a significant 

 difference between the values for one or more of these similar constants. 

 The constants for each distribution with the differences between the 

 similar constants in the two curves are given in Table XXVII. 



Table XXVII. — Mean, standard deviation, /3 1( and /3 2 , for the actual frequency distri- 

 bution of the position of dwarf eggs in the clutch compared with the same constants for 

 an equal even distribution with the same number of classes 



The last line of Table XXVII shows that not one of these constants 

 for the actual distribution differs significantly from the similar constant 

 for the ideal distribution — that is, the irregular fluctuations in clutch 

 position of dwarf eggs are not greater than would be expected to occur 

 from errors of sampling. The present data indicate, then, that a dwarf 

 egg is equally likely to occur in any clutch position. 



IX.— PHYSIOLOGICAL, CONDITIONS AND EFFECTIVE STIMULI WHICH 

 LEAD TO DWARF-EGG PRODUCTION 



It has been shown that dwarf eggs usually represent some temporary 

 disturbance or some accident in the physiology of reproduction, since 

 such eggs are preceded and followed by normal eggs. The disturbance 

 is most likely to occur during the height of the breeding season, although 

 it may happen at any time during the year. During any particular litter 

 or clutch a dwarf egg is equally likely to occur at any time. Although 

 the cause of dwarf-egg production is usually of a temporary character, 

 there are cases where a bird lays only, or chiefly, dwarf eggs for some 

 time. Other birds produce normal eggs for some time and then become 

 habitual dwarf-egg producers. In the present section we will consider 

 the nature of the disturbances, both temporary and permanent, which 

 lead to the production of dwarf eggs. 



Tiedemann (25) explained the origin of the dwarf eggs as the residue 

 of albumen and shell secreted in the oviduct at the end of the laying. 

 Wright (28) says that the occurrence of small abnormal eggs " need seldom 



