PART II. WEIGHT. 



Our statistics for size inheritance are not very satisfactory, because we 

 were unable to keep any considerable number of rabbits until they were 

 full grown, owing to the smallness of our breeding room, so that a large 

 number of weighings of adults is not available for purposes of compari- 

 son. But the size of a growing rabbit varies greatly with the character 

 of its food, and this in turn is dependent upon a variety of conditions 

 which it was not possible for us fully to control. A comparison of the 

 weights of growing rabbits at corresponding ages is, therefore, not alto- 

 gether satisfactory, yet it is the best material we have. 



In tables i to 25 the latest available weighing, or the heaviest weight, 

 is recorded for each rabbit. But since the weighings there recorded were 

 made at very different ages, it is necessary to select some particular age 

 at which to make comparisons. The age of 18 weeks has been selected, 

 because the weighings for that age are most numerous. 



In table 26 are shown the average weights, at 18 weeks of age, of 

 different lots of rabbits, each lot containing those of like ancestry. The 

 number of individuals in each lot is also shown in the table, as well as 

 the greatest range of variation in weight found in any litter of each lot. 

 The statistics in table 26 are fullest for those crosses (left section) in which 

 ordinary short-eared rabbits were concerned. The average weight of such 

 rabbits, in a lot of 17 individuals, is seen to be 1,412 grams. For lop- 

 eared rabbits it is something over 1,743 grams, the weight given in the 

 table from observations on 2 rabbits. This weight, however, has been 

 exceeded at 14 weeks of age by a majority of the lop-eared rabbits which 

 we have reared, so that it is certainly too low. 



The lots of rabbits, partly of short-eared, partly of lop-eared ancestry, 

 have intermediate weights, the weight tending to increase with increase 

 in the proportion of lop blood. The variability (range) in weight, which 

 was found to be twice as great in lop-eared as in short-eared rabbits, is 

 intermediate in the cross-bred lots, increasing with increase in the propor- 

 tion of lop blood. 



Both the position of the average for each lot, and the amount of variation 

 within it, indicate that weight-inheritance, like the inheritance of ear- 

 size, is blending in character. Neither dominance nor segregation in 

 the Mendelian sense are recognizable. 



The Belgian hare crosses and mixed crosses, recorded in the last sec- 

 tions of table 26, show, in general, results similar to those given by the 

 crosses with short-eared rabbits, but many of the averages are less reliable 



37 



