DWARF EGGS OF DOMESTIC FOWL. 



315 



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. Other birds produce normal eggs for some time 

 and then become "habitual" dwarf egg producers. In the 

 present section we shall consider the nature of the disturbances, 



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Fig. 55. Diagram showing the number of dwarf eggs which occurred 

 in each fifth of a litter. Dash line shows the mean frequency. 



both temporary and permanent, which lead to the production 

 of dwarf eggs. 



On the basis of unpublished data Pearl, Surface and Curtis 

 (loc. cit.) made a statement of the factors which were probably 

 involved in dwarf egg production. The data on which this 

 statement was based are included in the data used in the pres- 



