COAT CHARACTERS IN GUINEA PIGS AND RABBITS. 6l 



The smooth animals used in these matings were all pure-bred except 

 9 1338, which had a hybrid, R. (Sm.), father, but a pure-bred smooth 

 mother. We can not assume, however, that these hybrid rough ani- 

 mals formed in general weak rough gametes, for R. (Sm.) cJ 1 1111 had 

 in all, by smooth females, 13 rough offspring, but only in the mating 

 with 9 644 was a partial-rough individual produced ; again R. (Sm.) 

 c? 1 178 had rough offspring (6 in all) by three different smooth females, 

 but only in the mating with $ 1661 did he produce a partial-rough 

 animal. It would seem that the degree in which dominance is realized^ 

 in the zygote is dependent upon the relative potency of the gametes] 

 uniting, and that potency is apt to be more variable in the gametes oi/ 

 cross-bred than in that of pure-bred animals. If so, hybrid rough ani- 

 mals bred inter se, or with cross-bred rough or smooth individuals, 

 should produce an especially large proportion of partial-rough young. 

 The experiments made are as yet hardly extensive enough to give a 

 decisive answer to this question. 



Fully rough hybrid, R. (-Szw.), animals bred inter se, have produced 

 in all 32 rough young, only one of which is a partial-rough. This one 

 was produced by the following mating : 



R. (Sm.} J 1 mi X R. (Sm.) 9 1438, produced i R., i PR., 2 Sm. 



This same male, it will be remembered, produced a partial-rough indi- 

 vidual by the smooth female 644. 



We may return now to the question whether the condition of unusual 

 potency in the smooth gametes of animals producing partial-rough 

 young is handed on to the posterity of those animals. If the partial- 

 rough character of hybrid animals is due simply to : mperfectly realized 

 dominance of the character borne by the dominant gamete, and if the 

 characters united in the zygote maintain their distinctness and segre- 

 gate with the same relative potencies, when gametes are formed by 

 the hybrid as they possessed before, then we should expect to get fully 

 rough, as well as partial-rough offspring, by mating partial-rough 

 animals either inter se or with rough animals. The result of mating 

 partial-rough with smooth animals would depend upon the relative 

 potency of the gametes formed by the smooth mates ; if none of their 

 gametes were unusually potent, then the offspring should be half fully 

 rough and half smooth, without partial-rough young. But if half 

 the gametes formed by the smooth animals are unusually potent, then 

 the offspring should be visibly as i R. to i PR. to 2 Sm. 



