176 RAYMOND PEARL 



high as Li would alone. One Li cannot, however, build a super- 

 structure on another Li; nor can an L2 build one on another Li. 

 Of course it will be understood that with / (ab ence of female sex 

 and ovary) these physiological fecundity factors Li and L^ are 

 simply latent. 



Using the letters in the manner defined above, and with the 

 usual Mendelian method of writing gametic and zygotic formulae, 

 the data indicate the existence of Barred Plymouth Rock and 

 Cornish Indian Game males and females of the constitutions set 

 forth below. The only point needing particular attention in 

 reference to these formulae is that the factor Lo behaves in inher- 

 itance as a sex-limited character precisely like the barred color 

 pattern of the Barred Rock (40, 41). In consequence gametes of 

 the type FL2 are never formed. Any gamete which bears F 

 does not, under any circumstances, ever carry L^. 



It is not desirable to take the space to consider here all the 

 consequences which flow from the circumstance of the high fecun- 

 dity factor Lo being a sex-limited character. These matters will 

 be fully discussed farther on in the paper after the data them- 

 selves have been presented. Here it need only be said that since 

 L2 is a sex-limited character corresponding in behavior to the 

 barred color pattern, it means that & & may be formed with any 

 combination of the factors Li and L2, whereas 9 9 which bear Li 

 at all, must be heterozygotic in respect to it. Females may, 

 however, be either homozygotic or heterozygotic in respect to 

 Li, it not being a sex-limited character, and hence not in any 

 way coupled with or repelled by the factor F. That the female 

 fowl is heterozygotic in respect to the sex factor was suggested 

 by Spillman (50, 51) and has been demonstrated by the experi- 

 mental studies of Bateson (3), Goodale (12, 13), Hagedoorn (14), 

 Sturtevant (51) and Pearl and Surface (40, 41). 



Tables 5 to 8 inclusive show the constitution in respect to fecun- 

 dity of males and females of the breeds used in this work, as 

 indicated by the results obtained from breeding experiments. 

 These constitutions represent the 'Erbformeln' which flow from 

 the facts, and, in determination of their adequacy, are to l^e 

 tested against the facts. In these tables the columns headed 



