16 



Genetic Studies in Rabbits 



males in the earlier generation is accidental. In later generations, 

 though the numbers are small, the weights generally shew less fluctua- 

 tion and the females are consistently heavier^ 



When we come to the Flemish-mixed Fx generation the figures are 

 striking. The does average nearly 1| lbs. more than the bucks. In 

 view of the small number of the former it is not unlikely that this 

 difference would have been diminished had larger numbers been bred. 

 Nevertheless it is too substantial not to be regarded as having some 

 significance. The F^ generation is of much interest. In two out of the 

 four matings, viz. 39 x 41 and 223 x 222, the sexes average the 

 same weight, in one {N 230 x 41) the bucks average rather more than 

 the does, w^hile in the remaining one {N 230 x N 233) the average weight 

 of the does is very markedly greater than that of the bucks. The only 

 F^ mating was from two animals, % 0187 and c/ 192, both derived 

 from the F^ generation ex iV230 x iV233. 23 F4 animals were i^ised, 

 and here again the average weight of the does was markedly greater 

 than that of the bucks. 



In the case of the Flemish-Polish crosses the same phenomenon of 

 greater average weight among the does was noticed in the F^ generation 

 ex $ 138 X c/' Polish, while in that from J 203 x Polish the average 

 weight of the two sexes was nearly equal. It is possibly of significance 

 that in the former cross the Flemish doe (0 138) was a large one, and in 

 the latter a small one (0 203). 



Evidently we must recognise that in the rabbit a factor, or factors, 

 are to be found which bring about an increase of size in the doe as 



^ This is supported by the results from a further generation of three Flemish now being 

 reared. At the age of 10 pionths the c? weighed 6 lbs. oz. , while the two does were 

 respectively 6 lbs. 8 oz. and 6 lbs. 4 oz. 



