Chap. IV EFFECTS OF USE AND DISUSE. 131 



In the upper half of the following table I have given the measure- 

 ments of the skull often wild rabbits; and in the lower half, of 

 eleven thoroughly domesticated kinds. As these rabbits differ so 

 greatly in size, it is necessary to have some standard by which to 

 compare the capacities of their skulls. I have selected the length 

 of skull as the best standard, for in the larger rabbits it has not, as 

 already stated, increased in length so much as the body ; but as the 

 skull, like every other part, varies in length, neither it nor any other 

 part affords a perfect standard. 



In the first column of figures the extreme length of the skull is 

 given in inches and decimals. I am aware that these measurements 

 pretend to greater accuracy than is possible ; but I have found it 

 the least trouble to record the exact length which the compass gave. 

 The second and third columns give the length and weight of body, 

 whenever these observations were made. The fourth column 

 gives the capacity of the skull by the weight of small shot with 

 which the skulls were filled ; but it is not pretended that these 

 weights are accurate within a few grains. In the fifth column the 

 capacity is given which the skull ought to have had by calculation, 

 according to the length of skull, in comparison with that of the wild 

 rabbit No. 1 ; in the sixth column the difference between the actual 

 and calculated capacities, and in the seventh the percentage of 

 increase or decrease, are given. For instance, as the wild rabbit 

 No. 5 has a shorter and lighter body than the wild rabbit No. 1, we 

 might have expected that its skull would have had less capacity ; 

 the actual capacity, as expressed by the weight of shot, is 875 grains, 

 which is 97 grains less than that of the first rabbit. But comparing 

 these two rabbits by the length of their skulls, we see that in No. 1 

 the skull is 315 inches in length, and in No. 5 2'96 inches in length ; 

 according to this ratio, the brain of No. 5 ought to have had a 

 capacity of 913 grains of shot, which is above the actual capacity, 

 but only by 38 grains. Or, to put the case in another way (as in 

 column vn), the brain of this small rabbit, No. 5, for every 100 grains 

 of weight is only 4 grains too light, — that is, it ought, according 

 to the standard rabbit No. 1, to have been 4 per cent, heavier. I 

 have taken the rabbit No. 1 as the standard of comparison because, 

 of the skulls having a full average length, this has the least capacity ; 

 so that it is the least favourable to the result which I wish to show, 

 namely, that the brain in all long-domesticated rabbits has decreased 

 in size, either actually, or relatively to the length of the head and 

 body, in comparison with the brain of the wild rabbit. Had I taken 

 the Irish rabbit, No. 3, as the standard, the following results would 

 have been somewhat more striking. 



Turning to the table : the first four wild rabbits have skulls of the 

 same length, and these differ but little in capacity. The Sandon 

 rabbit (No. 4) is interesting, as, though now wild, it is known to be 

 descended from a domesticated breed, as is still shown by its pecu- 

 liar colouring and longer body ; nevertheless the skull has recovered 

 its normal length and full capacity. The next three rabbits are wild, 



