64 COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



If I have interpreted correctly the partial-rough animals obtained in 

 my experiments, they may be similar in nature to centripetally pig- 

 mented animals which lack some of the typical pigment patches, or 

 have only the eyes pigmented. A cross with albinos in which cen- 

 tripetal pigmentation is latent may serve to call the full set of coat spots 

 into activity, producing fully pigmented young, as we have already seen. 

 Similarly we may expect that crossing a partial-rough animal with a 

 smooth animal in which the rough character is fully latent would call the 

 rough character into full activity in the offspring. It remains, however, 

 to demonstrate the existence of smooth animals contain ing_/"w//y latent 

 the rough character. I have as yet no evidence of their existence other 

 than the slight excess of smooth animals over the expected proportion. 



HEREDITY OF LONG COAT. 



The longest or contour hairs of ordinary domesticated guinea-pigs, 

 like those of the wild Cavia apc>-ea, do not exceed a length of about 4 

 centimeters, but domesticated varieties with hair many times that length 

 are now well known. Where or when they originated is unknown ; 

 according to Cumberland they would seem to have been introduced into 

 England from France ; our American stocks probably came from Eng- 

 land. Long-haired smooth animals are commonly called "Angoras," 

 and long-haired rough ones " Peruvians." But the two sets of charac- 

 ters (long vs. short, and smooth vs. rough) are entirely independent of 

 each other, as we shall see, so that for the present we shall consider only 

 the length of the coat, irrespective of whether it is rough or smooth. 



My first experience with long-coated guinea-pigs was wholly un- 

 premeditated. In a family of short-haired guinea-pigs with which I 

 was experimenting and was practicing close-breeding, there appeared 

 several animals whose contour hairs were about twice as long as those 

 of their parents. These animals were all descended from a single pair 

 of short-haired guinea-pigs which had been purchased from a breeder, 

 but which I have no doubt had numbered among their ancestors a 

 long-haired animal. I found that the long-haired young bred true 

 inter se, which indicated that the long-haired character was recessive 

 in nature in relation to normal or short coat. This idea has been fully 

 confirmed by subsequent experiments, which were systematically insti- 

 tuted with the longest haired animals which I could secure. 



In studying the inheritance of this character, it is necessary to rear 

 the young to an age of about, two months before one can be sure 

 whether they are to have a normal coat, or one of more than normal 

 length. For at birth guinea-pigs of all sorts have hair of about the 

 same length (2 cm.). The coat of short-haired guinea-pigs reaches its 

 maximum length (about 4 cm.) not far from the age of one month, and 



