Since 1914, the writer has devoted himself at Kung-chu-ling, South Manchuria, China, to the improvement of the wool quality of mongolian sheep by crossing with merino sheep.Three types of ears are found in mongolian sheep, viz. large, small and rudimentary, while all merinos have large ears. The writer found the fact that the ear shapes of both mongolian and merino sheep are determined by only one Mendelian unit factor.The large ear, which is ordinarily found in mongolian sheep, is long, thin and drooping on both sides of the head. (See fig. 1.). The small ear, which is found in a small number of cases among mongolian sheep, is short, half-drooping, wedge-shaped and somewhat thicker than the large type. (See fig. 2). The rudi-mentary ear is a very small protuberance at ordinary ear place. (See fig. 3.) All of merino sheep have large ears.The dimensions of the ears described above are, respectively, as follows:The results of crossing sheep haviug the three types of ears above mentioned are shown in the following table:The results of these experiments show that the inheritance of ears in sheep is determined by a singlen Mendelian unit factor; thus the large and the rudimentary ear are both homozygous, while the small ear is heterozygous. These results obtained by the writer correspond with those obtained by Ritzman (1.3) in his experiments with native sheep at Hampshire and with those of Wriedt (4) with Norwegian sheep. In the case of mongolian sheep, however, one of the homozygotes has rudimentary ears, while in the case of the results obtained by Ritzman and Wriedt this is earless.Herepyolkin (5) writes, in his work "Karakul Sheep", that Karakul sheep have various shapes of ear, namely long drooping, short half-drooying, rudimentary, and even earless in some cases. Probably four types of ears exist in sheep, viz. large, small, rudimentary and earless.According to the results of the experiments of Ritzman and Wriedt, the large-eared and the earless sheep are both homozygous, and the small-eared sheep heterozygous. According to the results obtained by the writer, the large-eared and the rudimentary-eared sheep are both homozygous and the small-eared type heterozygous. Therefore, the experiment in inter-breeding of rudimentary-eared sheep and earless sheep is very interesting. It is to be regretted, however, that as the writer has no earless sheep, he can not proceed with this interesting experiment.