COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 59 



some fully rough and some partial-rough young by both males. From 

 these cases it seems clear that the production of partial- rough young 

 was due to some unusual potency of the gametes bearing the smooth 

 character, and that this potent character was inherent in all the gametes 

 formed by 9 2005, but in only about half of those formed by 9 2056. 

 If 9 208 was, as supposed, the mother of the 4 young, all partial-rough in 

 character, then she probably formed only potent gametes, as did 9 2005 

 apparently ; but if 9 208 and 9 99^ each produced some of the partial- 

 rough and some of the fully-rough young, then they were both similar in 

 character to 9 2056, as regards the formation of potent gametes. It 

 would seem probable, accordingly, that potency of the sort under consid- 

 eration is a function of the gametes ; that while most smooth females form 

 no potent gametes, some form 50 per cent and some 100 per cent of such 

 gametes ; or, in other words, that some smooth animals are purely potent, 

 others hybrid, as regards potency, but a majority non-potent. 



The question now arises, is this potency handed on from generation 

 to generation, i. ., do the gametes remain pure as regards potency, or 

 is their potency affected by a cross with the alternative and dominant 

 character, rough coat. There is some evidence in favor of both these 

 ideas. On one hand there is a manifest tendency for gametes to retain 

 from generation to generation any abnormal potency which they may 

 possess ; but on the other hand cross-breeding probably does frequently 

 alter the potency of recessive gametes. 



The first of the two ideas just mentioned receives support from the 

 admirable experiments of Coutagne ( : 02) with silk-moths, which 

 seem to have received less attention than is warranted by their great 

 richness in results and the care with which they have been executed. 

 Coutagne crossed two distinct races of silk-moths, one of which pro- 

 duced only white cocoons, the other only yellow cocoons. Dominance 

 apparently was alternative between the two characters, which seem to 

 have been nearly equal in potency, so that sometimes one, sometimes 

 the other dominated. The cocoons were 219 white in character, 240 

 yellow, without intermediates. Imagos hatching from either sort of 

 cocoon, when mated inter se, produced the other sort of cocoon, as 

 well as that from which they hatched, and approximately in the pro- 

 portions 3 of their own sort to i of the other. Thus, moths hatch- 

 ing from white cocoons mated inter se, and moths hatching from yel- 

 low cocoons mated inter se, produced in different lots 



From white cocoons : TOTAL. 



White 339 87 180 606 



Yellow 140 36 109 285 



From yellow cocoons : 



White 120 34 80 234 



Yellow 441 89 236 766 



