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MASS. EXPERIMENT STATION BULLETIN 344 



B. Character of the Ends of Eggs 



For convenience in these studies the pointed end of the egg away from the 

 air cell is designated as the "tip". The blunt end of the egg carrying the air 

 cell is called the "butt". The eggs of all birds were examined in February or 

 March and classified with respect to the character of the ends as rough, thin, 

 or normal. The shells of eggs designated as rough might or might not be very 

 porous in the end regions. Ends classed as thin were clearly very porous and 

 carried very little mineral coating over the membranes. 



In Table 7 are summarized the results in eight generations of daughters 

 produced in the three lines from the three different classes of dams. Dams of 

 each line were mated to full brothers on successive years to keep the male 

 ancestry as nearly uniform as possible. 



Table 7. — Character of Ends of Eggs 



With respect to egg tip character there is remarkable uniformity in the three 

 lines. The combined data show that the dams normal for shell tips produced 

 about 40 percent more normal daughters than did the group of 26 dams which 

 laid rough-tipped eggs. 



The character of shell butts does not vary widely in the three lines. Normal 

 dams produced about 38 percent more normal daughters than did mothers 

 showing the rough-butt character. 



These data in a general way indicate that heredity is in part responsible 

 for abnormal egg ends. Certainly the breeder should discriminate against 

 breeding birds whose eggs show abnormal ends. Eggs that have a rough 

 surface at one end are most likely to show the character at the other end also. 



