4s:> 



THE AMEBIC AX NATURALIST 



[Vol. L 



ei»\i*- production, is after all rather of the nature of a sep- 

 arate entity which may or may not be present, but which 

 when present operates to reduce the egg record of a hen 

 very materially. On the average, a hen's record for the 

 broody months is only about 60 per cent, of the same hen's 

 record for the non-broody months. There is always a 

 sharp break in monthly egg production with the onset of 

 the first broody period and as a hen once broody continues 

 as a rule to alternate brief periods of production with 

 broody periods, it follows that the number of eggs laid 

 depends in a large measure upon the number of broody 

 periods. 



Our viewpoint in regard to modifying factors for egg 

 production may be observed in morphological as well as 

 physiological characters. Thus, the color, arrangement 

 and length of hair could not be studied in a hairless race, 

 although the genes for color, arrangement and length may 

 actually exist in the germ plasm of the hairless individ- 

 uals. Variability in part at least is due to the existence of 

 numerous germinal factors which can come to somatic 

 expression only when some other germinal factor is pres- 

 ent. Thus, there are several types of rose comb which 

 appear to be due to definite factors that affect only the 

 rose comb. The spike, for example, may be telescoped 

 into the body of the comb. The telescoped condition is 

 clearly inherited but it does not appear in singles of the 

 same family, although there is no obvious reason why the 

 blade should not be telescoped quite as readily as the 

 spike. Before the rose comb can be said to be understood, 

 the various genetic modifying factors involved, their re- 

 lations to each other, and the mode of inheritance of each 

 must be made out. Any study of selection that fails to 

 take into account such internal modifying factors is in- 

 complete. 



There is no question regarding the inheritance of egg 

 production in the sense that certain families make much 

 better records than some other families, though in the 

 Rhode Island Reds the families that make the better 



