INHERITANCE OF EGG CHARACTERS 19 



Table 6. — Egg-Shell Texture of Mothers and Daughters 



*The "number of daughters" is the total of the rough, ridged, sandy, and normal. As indicated 

 in the text, those classed as "smooth" are made up of the "normal" and a part of the "ridged." 



Inheritance of Shell Texture 



Table 6 shows that dams laying ridged eggs with smooth surfaced shells 

 did not transmit the ridged shell character to any greater extent than did the 

 normal dams. Dams laying ridged and sandy eggs and dams laying sandy 

 eggs also produced about the same proportion of daughters laying ridged eggs 

 as dams laying either ridged-smooth or normal eggs. This fact would suggest 

 that the ridged shell condition does not depend upon inheritance. 



Dams laying eggs with sandy surfaces and carrying irregular ridges produced 

 generations of daughters that were very similar to those produced by dams 

 that laid eggs with sandy surfaces. Both groups of dams gave a significantly 

 lower percentage of daughters laying normal eggs than did ridged-smooth 

 mothers or normal mothers. It is probable that the granular or sandy surface 

 is due in part to genes recessive to normal. From a physiological standpoint 

 the production of eggs with sandy surfaces very frequently occurs in the first 

 year of laying following a prolonged period of high production in birds that 

 have laid normal eggs. Such a situation suggests that an exhaustion process 

 has taken place in the shell glands. The data in this experiment were collected 

 during February and March and do show a remarkable difference in the ability 

 of different birds to produce normal smooth shells. 



From the breeding standpoint these data indicate that breeding birds should 

 be selected for normal shell texture in order to establish this character in the flock. 

 The data further show that fewer daughters laying eggs with normal shell 

 texture were produced by the small-egg line A and that the medium-egg line 

 B gave the greatest number of daughters showing normal shell texture. 



