"Three animals crossihg the river" sanshouduhe 三獸渡河, a simile in which a rabbit, a horse, and an elephant appear to represent the distinction between the Three Vehicles, is one of the most famous similes in Buddhist literature. In Chinese Buddhist works, sanshouduhe quoted in Sengzhao 僧肇 (384?−414)'s Niepanwuzhilun 涅槃無知論, a chapter in the Zhaolun 肇論, is the first important occurrence. The simile was later repeatedly employed by many other authors. Tiantai Zhiyi 天台智顗 (538−597) also uses this simile to illustrate his doctrinal stance. However, the exact interpretation of the simile is not always the same. This is because sanshouduhe itself has different purposes, and it varies according to each sutra or sastra. There are several characteristics in the original meaning of sanshouduhe. The simile in the Puyaojing 普曜經 is thought to represent an early version. The meaning of “river” (河) is regarded as the Twelvefold Causes and Conditions in the Youposaijiejing 優婆塞戒經, the Apitanpiposhalun 阿毘曇毘婆沙論 and the Dabanniepanjing 大般涅槃經 chapter 23−1, although chapter 22−3 uses "Great nirvana" (大涅槃). The "bottom" (底) of the river depicted in the Youposaijiejing is quite similar to that of the Apitanpiposhalun being interpreted as vasana (習気), while the Dabanniepanjing chapter 22−3 regards the bottom as the insight into Buddha−nature. In spite of these differences, every sutra says that only the elephant is able to reach the bottom "completely" (盡). This last word may also mean perfect "extinction" of the vasana, especially in the Youposaijiejing and the Apitanpiposhalun. The "riverside" (岸) in the Dabanniepanjing chapter 23-1 is regarded as the insight into Buddha-nature, that is not yet reached by the Two lower Vehicles. In the Dabanniepanjing chapter 22-3, the two types of elephants appear to show the distinction between a Bodhisattva and the Buddha, instead of identifying the two, as in the Youposaijiejing and the Apitanpiposhalun. Zhiyi was familar with these characteristics of the simile and appropriately made some changes in his later lectures and works. Sandhouduhe mainly appears in relation to the Shared Teaching (通教) of the Four Teachings According to Content (化法四教). As Zhanran 湛然 (711-782) also pointed out, this is especially seen in the Mohezhiguan 摩訶止觀 and the Weimojingxuanshu 維摩經玄疏. When comparing with the characteristic of the Shared Teaching, the Youposaijiejing and the Apitanpiposhalun are close in content. On the other hand in the Weimojingxuanshu, we can find another version, which takes a stand on the Distinct Teaching (別教). It proclaims that only the Distinct Teaching Bodhisattva is able to gain an insight into Non-emptiness (不空) and Buddha-nature. Here the emphasis is on the difference from the Two Vehicles. In that respect, this use is close to the Dabanniepanjing chapter 23-1. Moreoverm in the Miaofalianhuajingxuanyi 妙法蓮華經玄義, like the Dabanniepanjing chapter 22-3, the two types of wlwphants appear. The small elelphant is like the Distinct Teaching Bodhisattva, whereas the large elephant is like the Perfect Teaching (圓教) Bodhisattva and is able to perfectly reach the very bottom which is the Reality (實相). Considering the circumstances mentined above, Zhiyi's usage of sanshouduhe is committed to his System of Stages of Practice, which developed in his later years. This simile was adopted not only in the Shared Teaching, but also in the Distinct and the Perfect Teachings. It is likely that the Concepts of Shared Advancing to Distinct (別開通) and Shared Advancing to Perfect (圓開通) were influential in this adoption. Although Zhiyi classified the teachings, through the usage of sanshouduhe he aimed to make the "river" the connecting point, and to establish a systematic structure between the Four Teachings and his System of Stages of Practice. Incidentally the Shared Teaching sanshouduhe was considered a quotation from the Dabanniepanjing in the Mohezhiguan. I surmise however, that this identification may