52 M. R. CURTIS AND RAYMOND PEARL 



the probability of getting credited with eggs she did not lay 

 was much smaller than in the preceding cases. Since the maxi- 

 mum diameter of the duct is much greater than a normal yolk 

 or the tumor it is possible that a few small yolks passed the 

 tumor and became the yolks of normal laid eggs. 



Bird No. 383 when killed was in normal laying condition, 

 with an egg in the shell gland and a series of five normal yolks 

 and four folicles in the ovary. There was no apparent ob- 

 struction to egg-laying. The peritoneum was normal and 

 transparent. As explained in the footnote to table 1, it is 

 probable that three eggs derived from the follicles on the ovary 

 had been laid on the floor of the pen. The other was still in 

 the duct. This bird's production record shows only three scat- 

 tered eggs and seven nesting records. At the time of autopsy 

 she was apparently in perfect health and capable of producing 

 eggs. Why she had failed to lay was not apparent. The idea 

 occurred to us that possibly she had been habitually laying on 

 the floor. Investigation of the floor egg record for the pen in 

 the laying house in which No. 383 had spent the year did not 

 indicate that this was the probable explanation. The total 

 number of eggs laid on the floor in this pen of 125 birds to March 

 1 was 92. This was not higher than the average number of 

 unrecorded eggs for a pen of that size, and was not as high as 

 many of the individual birds' trap-nest records. Also, the 

 attendants pick up all birds seen laying on the floor and a habitual 

 floor-layer is bound to be discovered in the long run. We must, 

 therefore, attribute the failure of No. 383 to lay to some obscure 

 physiological condition. 



That there can be no reasonable doubt that No. 383 was 

 genetically a high producer in constitution is shown by a careful 

 examination of her complete record in this respect. Her sire 

 was d^ No. 623; all his daughters, which were hatched before 

 June 1, with four exceptions to be noted below, made records 

 before March 1, of over 30 eggs each: 



