Studies of Inheritance in Lop-Eared Rabbits.

N 1909 CASTLE published some observations on the behavior of ear I length in crosses between lop-eared and ordinary varieties of rabbits, describing the inheritance as blending. Shortly thereafter LANG (191 I) applied to these observations the multiple factor hypothesis which had been formulated by NILSSON-EHLE on the basis of his studies of quantitative characters in oats and wheat. Since then, numerous studies of quantitative characters in animals and plants have served to establish firmly the multiple factor hypothesis. But no further study has been made of the peculiar ear character found in lop-eared rabbits. CASTLE has meanwhile shown that among other varieties of rabbits there is a close correlation between general body size and ear length, skull length, and leg length. During development, the body as a whole and its various parts grow faster lengthwise than transversely. So the general body form, and that of all elongated organs, becomes more slender as the absolute size increases. Accordingly, other things being equal, the larger the rabbit, the longer proportionally are its ears, its skull, and its legs. Lop-eared rabbits are one of the oldest recognized varieties of domestic rabbits and have undoubtedly attained their present excessive ear length as a consequence of long-continued selection. Other breeds of rabbits, for example Flemish Giants, exceed them in size of body, but none in length, width, and softness of the ears. This last characteristic (softness) they owe to a deficiency of cartilage in the ear, which makes it pliable and loppy and incapable of erection, as are the ears of ordinary rabbits. The body size of standard bred lop-eared rabbits is large, and that is one reason why their ears are long; but their ears are much longer than the ears in other breeds of rabbits of substantially the same body size. This shows that some additional agency operates to make the ears of lop-eared rabbits long. That i t is a genetic agency there can be no doubt, for lop-eared rabbits are known to be true breeding, and their peculiar character in crosses is transmitted equally through male and female individuals in the blending manner generally recognized as indicating the operation of multiple genes. In the light of what has been learned about heredity in the last highly fruitful quarter century, it has been thought desirable to make new observations on the results of crossing lop-eared rabbits with ordinary breeds of rabbits. To this end, in March 1932, a trio of purebred lop-eared rabbits was obtained from Mr. T. Corbishly, Secretary of the Lop-Eared