ROUGH FUR. 



117 



clear. The Lima stock shows a distinctly lower level of development 

 of roughness than is found in the 4-toe stock or even among the full- 

 roughs of tricolor stock. A large part of the variation and overlapping 

 in the remaining experiments in which various stocks have been mixed 

 is made intelligible by assuming that the residual heredity is unfavor- 

 able for roughness in the wild species and especially favorable in the 

 4-toe stock. If we let 2 + stand for favorable and S for unfavorable 

 residual heredity, the wild species and presumably the primitive 

 guinea-pigs are rrSSZ , while the good fancier's roughs, RRssS + 

 differ by at least three independent sets of factors, all favorable for 

 roughness. 



ROUGHNESS OF SERIES II. 



It has been mentioned that irregularities in hair direction have been 

 found in certain stocks which can not be classified by the grades which 

 have been defined. The BW race is a highly inbred race. No indi- 

 viduals of the pure stock have ever been observed to have roughness 

 on the face, back, or toes, but many of them show irregular partings 

 and crests along the chest and belly. It will be remembered that in 

 series I ventral roughness appears only in high-grade roughs grades 

 A or B. Thus the characteristic roughness of the BW stock is nearly 

 the least characteristic feature of series I. 



The only distinction which has been made in these BW roughs is 

 between strong-rough with two or more ridges and poor-rough with 

 only one ridge or a mere trace of roughness. Table 61 shows the 

 principal results. 



TABLE 61. 



It is clear that this roughness is due neither to a simple dominant 

 nor to a simple recessive. Aside from this, the results are exceedingly 

 difficult to interpret, since poor X poor gives more smooth than does 

 smooth by smooth. Probably the results will become more harmonious 

 when more data are obtained. It seems safe to conclude at present that 

 this roughness is wholly independent of ordinary roughness in its 

 causation. 



Irregularity in hair direction on the back, not resembling anything 

 in series I and not correlated with roughness of the hind toes, has 

 been observed in a few individuals of Arequipa and lea stock. It does 

 not seem to be like the BW roughness, but resembles the latter in the 

 irregularity of its inheritance. 



