The capacity of the osseous case of the brain is a more interesting point, to which I was led to attend by finding, as previously stated, that with all domesticated rabbits the length of the skull relatively to its breadth has greatly increased in comparison with that of the wild rabbits. If we had possessed a large number of domesticated rabbits of nearly the same size with the wild rabbits, it would have been a simple task to have measured and compared the capacities of their skulls. But this is not the case: almost all the domestic breeds have larger bodies than wild rabbits, and the lop-eared kinds are more than double their weight. As a small animal has to exert its senses, intellect, and instincts equally with a large animal, we ought not by any means to expect an animal twice or thrice as large as another to have a brain of double or treble the size.[27] Now, after weighing the bodies of four wild rabbits, and of four large but not fattened lop-eared rabbits, I find that on an average the wild are to the lop-eared in weight as 1 to 2·17; in average length of body as 1 to 1·41; whilst in capacity of skull they are as 1 to 1·15. Hence we see that the capacity of the skull, and consequently the size of the brain, has increased but little, relatively to the increased size of the body; and this fact explains the narrowness of the skull relatively to its length in all domestic rabbits. I II III IV Name of Breed WILD AND SEMI-WILD RABBITS. Length of Skull. Length of Body from Incisors to Anus. Weight of whole Body. Capacity of Skull measured by Small Shot. inches inches lbs ozs grains 1 Wild Rabbit, Kent 3·15 17·4 3 5 972 2 Wild Rabbit, Shetland Islands 3·15 — — 979 3 Wild Rabbit, Ireland 3·15 — — 992 4 Domestic rabbit, run wild, Sandon 3·15 18·5 — 997 5 Wild, common variety, small specimen, Kent 2·96 17·0 2 14 875 6 Wild, fawn-coloured variety, Scotland 3·10 — — 918 7 Silver-grey, small specimen, Thetford warren 2·95 15·5 2 11 938 8 Feral rabbit, Porto Santo 2·83 — — 893 9 Feral rabbit, Porto Santo 2·85 — — 756 10 Feral Rabbit, Porto Santo 2·95 — — 835 Average of the three Porto Santo rabbits 2·88 — — 828 DOMESTIC RABBITS. 11 Himalayan 3·50 20·5 — 963 12 Moscow 3·25 17·0 3 8 803 13 Angora 3·50 19·5 3 1 697 14 Chinchilla 3·65 22·0 — 995 15 Large