OLD TYPES AND NEW 171 



/ = an intensity factor which determines the degree of 

 pigmentation. It can be transmitted indepen- 

 dently of C through an albino. Discovered by 

 Bateson and Durham in 1906. 



i = the absence of intensity or dilution. Dilute black = 

 blue. Dilute yellow = cream. Dilute gray = 

 blue-gray. 



U = SL factor for uniformity of pigmentation or " self- 

 color" discovered by Cuenot in 1904. 



u = the absence of uniformity which results in spotting 



with white. 

 A = Si pattern factor for agouti, or wild gray color, which 

 causes the brown and black pigments to be ex- 

 cluded from certain portions of each hair, resulting 

 in the gray coat. When present in the rabbit, it 

 is also associated with white or lighter color on 

 the under surfaces of the tail and belly. It was 

 demonstrated bv Castle in 1907. 



a = the absence of the agouti or pattern factor. 



7. The Kinds of Gray Rabbits 



Each of the apparent kinds of gray rabbits indicated 

 in the foregoing table may be made up of various 

 genotypes. For instance, there are thirty-two differ- 

 ent genotypes, each of which is phenotypically a gray 

 rabbit. The zygotic formula for each of these thirty- 

 two possibilities is displayed in the next table, and it 

 will be seen that these range all the way from rabbits 

 homozygous in all their variable characters (No. 1) 

 to those homozygous in none (No. 3'2). 



The progeny of these various types of gray rabbits 

 when inbred wall consequently vary from the pure 



