LINKAGE 71 
large number of species in which Mendelian inheri- 
tance has been discovered; but there are several rea- 
sons why more cases have not been recorded. In 
the first place, the number of chromosomes is generally 
large compared with the number of characters that 
Fig. 27.—Barred Plymouth Rock female by Langshan male. Compare 
similar cross in Abraxas for scheme of inheritance. 
have been studied in such a way that linkage would 
be noticed. Thus, there is little chance of finding 
two factors lying in the same chromosome. Sec- 
ondly, unless this linkage is close, it might easily 
escape detection, especially when the number of off- 
