COLOR AND COAT CHARACTERS. 39 



preponderance of probability would allow the same conclusion in this 

 case; hence it is not an unreasonable assumption to conclude that the 

 total of 10 rough young from these matings corroborates a fact which 

 has been firmly established by 249 rough offspring in experiments 

 on the guinea-pig (Castle, 1905). In this light it would have been 

 surprising if the rough guinea-pig males had not shown themselves 

 dominant. 



HETEROZYGOUS ROUGH ANIMALS CROSSED WITH SMOOTH ANIMALS. 



The method of procedure in the discussion of color characters has 

 been to consider first the homozygous form of a character in crosses, 

 and since the wild is homozygous in all characters except roughness, 

 the chronological sequence of crosses has heretofore been fairly parallel 

 with the order of discussion. In the case of roughness this is not so, 

 for the wild form was not mated to any homozygous rough animals; 

 hence the discussion began with dilute-blooded hybrids in table 56. 

 Nevertheless the experiments with the rough character were the very 

 first in order of time, for the two female guinea-pigs which were first 

 mated to a wild male ( d^ 1) were heterozygous rough animals. If these 

 two females, 9 1125 and 9 1625, had been mated to a smooth guinea- 

 pig male they would have produced about equal numbers of rough and 

 smooth animals. When mated to the wild male they did precisely the 

 same, for half their gametes carried the rough and half carried the smooth 

 character, whereas all of the wild gametes produced by cf 1 carried only 

 the smooth character, and the union of such gametes resulted in 4 rough 

 and 7 smooth offspring (table 57). The departure from the most 

 probable expectation is 1 or 2 individuals. 



This result would indicate that mating a smooth wild C. rufescens 

 with a rough tame guinea-pig gives the same result as similar matings 

 among guinea-pigs. In a measure it is true. The wild do not carry 

 roughness, and the tame guinea-pig has acquired a progressive domi- 

 nant variation, but the dominance of this rough character is very 

 incomplete. The ^ wild offspring from the two matings showed a 

 degree of roughness which would almost escape attention. Just a 

 very slight ridge of reversed hair on the back or even only a few reversed 

 hairs on the toes was all that would indicate the maternal contribution. 

 Just exactly why the smooth wild thus inhibits the full expression of a 

 dominant tame rough character must be a matter of conjecture. A 

 similar behavior of the rough character in crosses with certain smooth 

 guinea-pig individuals was noted by Castle (1905). 



With the gradual reduction of wild blood in later hybrid generations, 

 the rough character of the hybrids reached the full number of rosettes 

 which is seen in the tame. It may be misleading to state it in that 



