106 



INHERITANCE IN GUINEA-PIGS. 



ulated are those in which the rough is known to be Rr because of 

 a smooth parent, or because of a smooth young one in 6 or more. 

 Expectation is here 1 to 1. The remaining cases of rough by smooth, 

 in which expectation is still probably not far from 1 to 1, are also 

 given. 



These results are in harmony with the view that rough differs from 

 smooth by a dominant unit factor. 



INHERITANCE OF MAJOR VARIATIONS. 



Before giving any hypotheses, it will be well to present the experi- 

 mental results with the immediate deductions which can be drawn 

 from them (tables 46 to 55) . 



(1) In some stocks there is very little variation in the rough char- 

 acter and there is a wide gap between the lowest rough and smooth. 

 The 4-toe stock is an excellent example of such a stock. It is worthy 

 of note that we get a similar result in the Lima stock if we exclude the 

 litters of L6, L24, L56, and L99. Female L6, smooth, was one of the 

 original 8 in the Lima stock. Female L24, smooth, was her daughter. 

 Female L56, rough C, was the daughter of L24, and male L99, rough C, 

 was the son of L56. Most of the tame guinea-pig stocks (BW, dilute 

 selection) seemed to be like the 4-toe stock in the above respect when- 

 ever rough was introduced into them in a cross. 



TABLE 46. 



Most of those graded rough A or rough B above must be heterozy- 

 gous. As nothing higher than rough A appeared in the crosses A X A 

 and B X B, it seems clear that the homozygotes in these stocks at 

 least are no more rough than the heterozygotes, i. e., dominance is 

 complete. 



(2) When a wild species of Cavia (smooth), or a smooth of certain 

 tame stocks is crossed with a full-rough, the rough young are of low 

 grade rough C or D. 



