332 



THE EFFECTS OF CONDITIONS 



"skull capacity" may be more or less closely corre- 

 lated with some other character which has been the ob- 

 ject of selection, and so have been thereby uninten- 

 tionally modified. In the accompanying table are 

 given the mean values of Darwin's measurements:* 



The weight of most breeds of domestic rabbit is not 

 much greater than that of wild ones, but that of the 

 lop-eared variety is more than twice as great. The 

 length of body was measured from incisors to anus, 

 whilst the capacity of the skull was determined by 

 weighing the small shot taken to fill it (the numbers 

 given in the table being the weight in grains). Tak- 

 ing the relation of capacity of skull to length of body 

 in the wild rabbit as 100, we see that, on an average, 

 the skull capacity of the domestic rabbit is about 20 per 

 cent. less. That of the Porto Santo rabbit is, on the 

 other hand, very slightly greater. 



The diminution in the size of the rabbit's brain is at- 

 tributed by Darwin, to the effects of disuse, and 



* " Animals and Plants," i. p. 133. 



