EXPERIMENTAL. 



27 



The number of individuals in a litter might seem to influence the 

 growth of the young at a critical period by the limit of the amount of 

 milk received, but it is probable that there is a correlation between the 

 production of milk and the number in the litter. If the sizes of the 

 rabbits in different litters from the same parents are compared, different 

 bones tell different stories. It may be noted, however, that when there 

 are two litters of over four animals from the same parents their dis- 

 tributions are very similar for most characters. But even if rabbits 

 of a large litter are under a disadvantage due to a scarcity of milk, 

 we have seen that unfavorable conditions do not leave a permanent 

 effect, and if the growth is slower at first it will be more rapid later when 

 the animals eat the regular food, yet it may take several months for 

 the animals to recover entirely; this is especially true of young animals. 

 When the rate of growth is very rapid normally it takes longer for any 

 loss to be repaired. To find a possible correlation between the size 

 of the litter and the length of bones, averages of litters of four and less 

 were compared with averages of litters of five and more (see table 1). 

 In 12 litters of 4 and less were 42 rabbits; in 14 litters of 5 and more 

 were 90 rabbits. The averages of a character for the large and for the 

 small litters in each family were first found; then the grand averages 

 of all the small and of all the large litters. In this way the different 

 family sizes were taken into account. Grand averages were found for 

 eight characters: five of these show the averages for the larger litters 

 from 0.043 cm. to 0.002 cm. less than the averages of the smaller litters; 

 one showed no difference ; the other two gave averages for the smaller 

 litters that were 0.044 cm. and 0.021 cm. less than the averages of the 

 large litters (see table 1). The sum of the plus differences is 0.065, that 

 of the minus differences is 0.087. Thus it is seen that there is no very 

 marked difference that can be ascribed to the number in the litter. 



Table 1 . — Comparison of large and small litters as regards average bone measurements. 



The season of birth may be supposed to influence the early growth 

 of the animals, but as the period of nursing is long this influence is 

 probably very slight. Most of the animals were born between March 

 and September; this probably has little significance, as the matings were 



