FERTILITY IN ANIMALS 563 
Conclusion.—We may conclude, therefore, fairly, that fertility in 
animals is a complex character highly modifiable under different con- 
ditions of environment, but nevertheless possessing a definite, although 
intricate and obscure, factorial basis. The character bears the same 
relation to systems of breeding as do any other characters, that is, the 
system of breeding in itself has no effect upon it, it is merely a mode of 
achieving certain results. This is clearly established by Pearl’s experi- 
ments on fecundity in fowls, for they demonstrate that factors for high 
fecundity exist, and that these factors behave like other Mendelian 
factors. 
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