SEX INHERITANCE 109 
In certain sheep, such as some races of Merinos 
(Fig. 36 A), the horns are present only in the ram. 
If a young ram is castrated his horns fail to grow. 
To study the inheritance of the factors involved in 
this difference it would be necessary to use for 
crossing with Merinos a different breed in which 
the horns were present (or absent) in both sexes, 
but such an experiment has not been made. There 
i 
Fig. 36A.—Merino sheep of Rambouillet. Ram horned, ewe hornless. 
are other breeds of sheep in which both sexes are 
hornless (Suffolks), and still other breeds in which 
both sexes are horned, those of the ram being 
larger (Dorsets) (Fig. 36 B). The two latter have 
been crossed. It may be that we are dealing here 
either with factors for horns different from those 
in Merinos, or that modifying factors cause the 
different conditions. In this cross (Fig. 36 C) 
therefore it can not be said that we are studying 
