R. C. PUN^ETT 223 



The F, generation. 



The experiments were staited with three yellow Dutch rabbits 

 (? 1, ? 2, and ^ 5), three tortoise Dutch ( ? 3, ? 4, and ^ 6), and 

 two Hiinalayans ( ? 7 and ^ 8). As a description of these breeds is 

 readily accessible in any work dealing with fancy rabbits it is unneces- 

 sary to say more than that the animals used were in each case fair 

 specimens of their respective breeds. It should however be mentioned 

 that each of the three yellows turned out to be heterozygous for the 

 recessive tortoise. This was not only indicated when they were crossed 

 with the Himalayan, but was shewn to be the case by breeding them 

 together and by crossing them with the tortoise. Thus : 



Yellow ? 1 X yellow i 5 gave 12 yellows and 2 tortoise 

 Yellow (J 5 X tortoise ?3 gave 2 ,, 3 ,, 



The t(jrtoises when bred together gave only tortoise. 



The cross between the yellow and the Himalayan was made in three 

 cases with the following results : 



Agouti Black 



Yellow ? 1 X Himalayan i 8 gave 7 6 



„ f2 X „ <?8 „ 5 6 



„ <?5 X „ ?7 „ 2 3 



Totals ... 14 15 



The black Himalayan, though recessive as far as pattern is concerned, 

 supplies the factor for extension of colour (E), and as the yellows were 

 all heterozygous the expectation from such crosses is equal numbers of 

 agoutis and blacks. This expectation, as the F^ figures shew, is closely 

 realised. 



Since the tortoise does not contain the agouti factor (A) the natural 

 expectation from the ci-oss between tortoise and Himalayan is blacks 

 only. This, as the figures shew, was actually realised experimentally : 



Tortoise ? 3 x Himalayan <J 8 gave 4 blacks 

 ,, ?4 X „ i^ „ 21 „' 



Total ... 25 ,, 



The F. (feneration, from the F^ agoutis. 



The reversionary agoutis from the manner of their making must 

 be heterozygous both for the agouti factor (A) and for the intensity 

 factor (E). Hence when bred together they should give agoutis, blacks, 

 yellows, and tortoises in the ratio 9:3:3:1. At the same time one- 

 quarter of their offspring should be Himalayans. Five F^ does were 



16—2 



