FECUNDITY IN RHODE ISLAND 



RED BREED OF DOMESTIC FOWL' 



Important Question of Why Some Hens Lay Many More Eggs Than Others 



A Trait that Is Doubtless Inherited, but Is Transmitted 

 Differently in Different Breeds 



DR. H. D. GOODALE has been 

 putting to a test Dr. Raymond 

 Pearl's well-known theory for 

 excessive egg production in 

 fowl. Pearl worked with Barred Ply- 

 mouth Rocks, where he found high 

 fecundity to be essentially dependent 

 on a sex-linked factor contributed by 

 the male. 



Of Pearl's theory, Babcock and Clau- 

 sen^ make the following highly co-m- 

 plimentary comment : "It is a genuine 

 pleasure in a mass of contradictory and 

 illy digested data to meet with some- 

 thing which gives hope for the same 

 definiteness with regard to the prob- 

 lem of the inheritance of fecundity 

 that has been attained in the analysis of 

 the inheritance of other more clearly de- 

 fined chajracters. We cannot, there- 

 fore, but commend the patient investi- 

 gation and brilliant analysis to which 

 Pearl has subjected the problem of the 

 inheritance of fecundity in the domes- 

 tic fowl. Many criticisms have been 

 launched against his conclusion, it is 

 true, but it is highly probable that these 

 criticisms involve a fundamental mis- 

 conception of the nature and results of 

 scientific knowledge." 



Dr. Goodale, writing m the American 

 Naturalist for June-July, 1918, does not 

 criticise the general value of Pearl's 

 theory, but finds the conditions some- 

 what difTerent for fecumdity among 

 Rhode Island Reds. Part of Dr. Good- 

 ale's conclusions are the following: 



SELECTION 



Pearl's success in securing increased 

 egg production by breeding might be 

 due to his methods of selecting the 



breeders, regardless of all theoretical 

 considerations. Families that contained 

 all high producers were selected gener- 

 ation after generation to propagate the 

 high fecundity lines. Families in which 

 true mediocre producers appeared, i. e., 

 where segregation took place, were not 

 used in breeding for increased egg pro- 

 duction. This type of selection could 

 hardly fail to yield results, provided that 

 egg production is inherited. Neverthe- 

 less, it is clear that fecundity is inher- 

 ited in Mendelian fashion in Pearl's 

 Barred Plymouth Rocks. However, 

 the results obtained by Dryden alt the 

 Oregon Station show that individual se- 

 lection in pedigreed lines as opposed to 

 mass selection may result in improved 

 egg production quite as well as by the 

 application of Pearl's theory. 



Egg production in the domestic fowl 

 may seem at first sight to be a highly 

 desirable cha^riacter on which to study 

 the influence of selection. It may be 

 regarded as a unit character if one so 

 desires, and if, by selection, this char- 

 acter is changed, it is clear that selec- 

 tion has been elTective. But it is also 

 clear that the effectiveness of such se- 

 lection in this instance rests, in large 

 measure, at least, upon the influence 

 exerted by various modifying factors, 

 such as broodiness or age at first egg, 

 discussed in this paper. It is possible 

 to study these factors individually both 

 by themselves and also in their relation 

 to egg production. Broodiness is known 

 to behave like a Mendelian dominant, 

 while Pearl has shown that the rate 

 of production during the winter cycle 

 is dependent on two genes, one sex- 



1918. 



1 Babcock, E. B., and Clausen, R. E. Genetics in Relation to Agriculture. New York, 



333 



