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 $431, own brother to d 1 176, was likewise mated with 

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

 of his brother (^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 ( d 1 678) 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 litter. 

 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 litters 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 



