COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



SUMMARY. 



(1) There occur among domesticated guinea-pigs three pairs of alter- 

 native coat-characters which conform in their inheritance to Mendel's 

 law of heredity. These are (i) albinism, which is recessive with respect 

 to pigmented coat ; (2) smooth coat, which is recessive with respect to 

 rough coat ; and (3) long coat, which is recessive with respect to short 

 coat. Two of the recessive characters, viz, albinism and long coat, are 

 doubtless characters of comparatively recent origin, which have made 

 their appearance since the guinea-pig was domesticated. The third 

 recessive character, smooth coat, is undoubtedly ancestral, and curiously 

 enough is regularly dominated by rough coat, a character probably of 

 recent origin, for a cavy bearing rosettes like those of the " Abyssinian " 

 guinea-pig is unknown in a wild state. This indicates that ancestral 

 characters are not necessarily dominant over new characters in heredity. 

 The three pairs of characters are probably wholly uncorrelated. 



(2) In rabbits occur two of the three pairs of alternative coat-charno 

 ters which are found in guinea-pigs. Here, too, albinism and long or 

 "angora" coat are recessive characters. A resetted or rough coat is 

 unknown in rabbits. 



(3) A sharp distinction must be made between characters which 

 are recessive and those which are latent. Recessive characters dis- 

 appear from an individual in which they are associated with the 

 corresponding dominant character, yet they reappear distinct in half 

 the gametes formed by that individual ; latent characters are characters 

 normally dominant, which have disappeared in recessive gametes 

 beyond hope of recall, except under conditions of cross-breeding which 

 are in most cases not entirely clear. Albino gametes transmit in a 

 latent condition both specific pigment characters and specific color- 

 patterns. These latent characters can be brought into activity only by 

 cross-breeding with a pigmental animal. The rough coat-character 

 may likewise become almost completely, if not quite completely, latent 

 in smooth animals. These facts indicate a possible explanation of the 

 observed slight excess of recessives over the Mendelian expectation in 

 cases involving one or the other of these two pairs of characters. In 

 the case of the long vs. short pair of characters, an excess of recessives 

 and the occurrence simultaneously of intermediates in generation F 2 , 

 but not in F n are more probably due to imperfect segregation than to 

 latency of the dominant character. It is possible, however, that partial 

 latency and imperfect segregation are related, if not identical phenomena. 



