| Name of Breed. | I. | II. | III. | IV. | V. | VI. | VII. |
| inches. | inches. | lbs. ozs. | grains. | grains. | grains. | ||
| 1. Wild rabbit, Kent | 3.15 | 17.4 | 3 5 | 972 | .. | .. | |
| 2. " Shetland Islands | 3.15 | .. | .. | 979 | .. | .. | |
| 3. " Ireland | 3.15 | .. | .. | 992 | .. | .. | [2 per cent. too heavy in comparison with No. 1.] |
| 4. Domestic rabbit, run wild, Sandon | 3.15 | 18.5 | .. | 977 | .. | .. | |
| 5. Wild, common variety, small Specimen, Kent | 2.96 | 17.0 | 2 14 | 875 | 913 | 38 | 4 per cent. too light. |
| 6. Wild, fawn-coloured variety, Scotland | 3.1 | .. | .. | 918 | 950 | 32 | 3 " " |
| 7. Silver-grey, small specimen, Thetford warren | 2.95 | 15.5 | 2 11 | 938 | 910 | 28 | 3 " too heavy. |
| 8. Feral rabbit, Porto Santo | 2.83 | .. | .. | 893 | 873 | 20 | 2 " " |
| 9. " " | 2.85 | .. | .. | 756 | 879 | 123 | 16 " too light. |
| 10. " " | 2.95 | .. | .. | 835 | 910 | 75 | 9 " " |
| Average of the three Porto Santo Rabbits | 2.88 | .. | .. | 828 | 888 | 60 | 7 " " |
| Domestic Rabbits | |||||||
| 11. Himalayan | 3.5 | 20.5 | .. | 963 | 1080 | 117 | 12 " " |
| 12. Moscow | 3.25 | 17.0 | 3 8 | 803 | 1002 | 199 | 24 " " |
| 13. Angora | 3.5 | 19.5 | 3 1 | 697 | 1080 | 383 | 54 " " |
| 14. Chinchilla | 3.65 | 22.0 | .. | 995 | 1126 | 131 | 13 " " |
| 15. Large lop-eared | 4.1 | 24.5 | 7 0 | 1065 | 1265 | 200 | 18 " " |
| 16. " " | 4.1 | 25.0 | 7 13 | 1153 | 1265 | 112 | 9 " " |
| 17. " " | 4.07 | .. | .. | 1037 | 1255 | 218 | 21 " " |
| 18. " " | 4.1 | 25.0 | 7 4 | 1208 | 1265 | 57 | 4 " " |
| 19. " " | 4.3 | .. | .. | 1232 | 1326 | 94 | 7 " " |
| 20. " " | 4.25 | .. | .. | 1124 | 1311 | 187 | 16 " " |
| 21. Large hare-coloured | 3.86 | 24.0 | 6 14 | 1131 | 1191 | 60 | 5 " " |
| 22. Average of above seven large lop-eared rabbits | 4.11 | 24.62 | 7 4 | 1136 | 1268 | 132 | 11 " " |
| 23. Hare (L. timidus) English specimen | 3.61 | 7 0 | 1315 | ||||
| 24. " " German specimen | 3.82 | 7 0 | 1455 |
I have previously remarked that, if we had possessed many domestic rabbits of the same average size with the wild rabbit, it would have been easy to compare the capacity of their skulls. Now the Himalayan, Moscow, and Angora rabbits (Nos. 11, 12, 13 of Table) are only a little larger in body, and have skulls only a little longer, than the wild animal, and we see that the actual capacity of their skulls is less than in the wild animal, and considerably less by calculation (column 7), according to the difference in the length of their skulls. The narrowness of the brain-case in these three rabbits could be plainly seen and proved by external measurement. The Chinchilla rabbit (No. 14) is a considerably larger animal than the wild rabbit, yet the capacity of its skull only slightly exceeds that of the wild rabbit. The Angora rabbit, No. 13, offers the most remarkable case; this animal in its pure white colour and length of silky fur bears the stamp of long domesticity. It has a considerably longer head and body than the wild rabbit, but the actual capacity of its skull is less than that of even the little wild Porto Santo rabbits. By the standard of the length of skull the capacity (see column 7) is only half of what it ought to have been! I kept this individual animal alive, and it was not unhealthy nor idiotic. This case of the Angora rabbit so much surprised me, that I repeated all the measurements and found them correct. I have also compared the capacity of the skull of the Angora with that of the wild rabbit by other standards, namely, by the length and weight of the body, and by the weight of the limb-bones; but by all these standards the brain appears to be much too small, though in a less degree when the standard of the limb-bones was used; and this latter circumstance may probably be accounted for by the Limbs of this anciently domesticated breed having become much reduced in weight, from its long-continued inactive life. Hence I infer that in the Angora breed, which is said to differ from other breeds in being quieter and more social, the capacity of the skull has really undergone a remarkable amount of reduction.
From the several facts above given,—namely, firstly, that the actual capacity of the skull in the Himalayan, Moscow, and Angora breeds, is less than in the wild rabbit, though they are in all their dimensions rather larger animals; secondly, that the capacity of the skull of the large lop-eared rabbits has not been increased in nearly the same ratio as the capacity of the skull of the smaller wild rabbits has been decreased; and thirdly, that the capacity of the skull in these same large lop-eared rabbits is very inferior to that of the hare, an animal of nearly the same
size,—I conclude, notwithstanding the remarkable differences in capacity in the skulls of the small P. Santo rabbits, and likewise in the large lop-eared kinds, that in all long-domesticated rabbits the brain has either by no means increased in due proportion with the increased length of the head and increased size of the body, or that it has actually decreased in size, relatively to what would have occurred had these animals lived in a state of nature. When we remember that rabbits, from having been domesticated and closely confined during many generations, cannot have exerted their intellect, instincts, senses, and voluntary movements, either in escaping from various dangers or in searching for food, we may conclude that their brains will have been feebly exercised, and consequently have suffered in development. We thus see that the most important and complicated organ in the whole organization is subject to the law of decrease in size from disuse.
Finally, let us sum up the more important modifications which domestic rabbits have undergone, together with their causes as far as we can obscurely see them. By the supply of abundant and nutritious food, together with little exercise, and by the continued selection of the heaviest individuals, the weight of the larger breeds has been more than doubled. The bones of the limbs have increased in weight (but the hind legs less than the front legs), in due proportion with the increased weight of body; but in length they have not increased in due proportion, and this may have been caused by the want of proper exercise. With the increased size of the body the third cervical vertebra has assumed characters proper to the fourth cervical; and the eighth and ninth dorsal vertebræ have similarly assumed characters proper to the tenth and posterior vertebræ. The skull in the larger breeds has increased in length, but not in due proportion with the increased length of body; the brain has not duly increased in dimensions, or has even actually decreased, and consequently the bony case for the brain has remained narrow, and by correlation has affected the bones of the face and the entire length of the skull. The skull has thus acquired its characteristic narrowness. From unknown causes the supra-orbital processes of the frontal bones and the free end of the malar bones have increased in breadth; and in the larger breeds
the occipital foramen is generally much less deeply notched than in wild rabbits. Certain parts of the scapula and the terminal sternal bones have become highly variable in shape. The ears have been increased enormously in length and breadth through continued selection; their weight, conjoined probably with the disuse of their muscles, has caused them to lop downwards; and this has affected the position and form of the bony auditory meatus; and this again, by correlation, the position in a slight degree of almost every bone in the upper part of the skull, and even the position of the condyles of the lower jaw.