30 



INHERITANCE IN RABBITS 



The offspring fluctuate in ear-length about the mid-parental condi- 

 tion; 2 of them exceed it, 3 fall short of it. The minus deviations, how- 

 ever, are greater than the plus ones, precisely as in lop-eared rabbits bred 

 inter se (p. 17). The range of variation is 17 mm., which is greater 

 than that occurring among short-eared rabbits, but less than that occur- 

 ring among lop-eared rabbits. 



Another son of 9431, own brother to J' 176, was Ukewise mated with 

 his mother. This male (177, cross 3) had ears 10 mm. shorter than those 

 of his brother (d'176). The mid-parental ear-length, accordingly, was 

 only 137 mm. Two young only were reared to an age of 20 weeks, and 

 each of them had an ear-length of 125 mm. 



Further tests of the half-blood lop females 175 and 178 are afforded 

 by the crosses recorded in table 20, with a related three-quarter-blood 

 lop male (319) produced by cross 4. 



Table 20. 



The young produced by mating i are all intermediate in ear-length 

 between their parents. One ( 9 674) exactly attains at 20 weeks of age 

 the mid-parental ear-length, a second ( s 678) would doubtless have done 

 so had he not fallen into bad condition at about 13 weeks of age. Previous 

 to that he had been one of the largest and longest-eared rabbits in the htter. 

 Of the remaining 2, both of which developed normally and were of large 

 size at 20 weeks of age, one exceeded the mid-parental ear-length by 7 mm. 

 and the other fell 10 mm. short of it, approaching to within 5 mm. of the 

 ear-length of the short-eared parent. The range of variation (17 mm.) is 

 not excessive, and the result may be described as a fully normal blend, with 

 no indication of heterogeneity among the gametes of the cross-bred parents. 



Mating 2 yielded 2 htters very different in character and illustrating 

 rather strikingly the influence of external conditions on growth. Litter 

 I consisted of 2 young only. They were born in summer and developed 

 under optimum conditions as regards food supply. At 20 weeks of age 

 they had attained large size and had ear-lengths exceeding by 6 and 10 



