52 



SIZE INHERITANCE IN RABBITS. 



the growth of the body as a whole. What makes the difference between 

 a big rabbit and a small one is clearly a quantitative difference in these 

 general factors, or it is something which modifies the action of these 

 general factors, which amounts to the same thing. That which deter- 

 mines the adult size of a rabbit determines (if other conditions remain 

 constant) both the rate at which it grows and the time when growth 

 ceases. A large race of rabbits has a steeper growth curve than a 

 small race and the period of growth continues longer (see Castle et al., 

 1909). The proportions of the body also change in a constant direction 

 as growth proceeds. For example, the larger a rabbit becomes the more 

 elongated its skull becomes. Is a larger size attained in one race simply 

 because growth continues longer, or is the character of growth different 

 from the beginning? A study of immature rabbits of large and small 

 races at corresponding absolute size stages might throw light on this 

 question. 



Table 9. — Correlation between tlie measurements 0. M. and Zp. in the rabbits studied. 



r -=0.750. 



Table 10. — Correlation between the measurements O. M. and II. r -0.743. 



