This paper analyses the different phonological strata of first division unrounded finals of the Xiè Rhyme Group （蟹攝），specifically the Xai rhyme and Tài rhyme, in the finals system of proto-Min and explores the distinction between double rhymes in old Jiangdong dialects. Norman (1981) reconstructed five finals for Xai rhyme and Tài rhyme. They are:
*əi for Xai 菜咍栽咍來咍
*oi for Xai 袋咍
*ɑi for Tài 帶泰蔡泰蓋泰
*uəi for Xai 改咍
*yəi for Xai 開咍
According to Norman’s reconstruction, there are four finals for the Xai rhyme but there is only one final for the Tài rhyme. Therefore, some issues need to be clarified. To begin with, what is the time sequence of those four forms of Xai? Additionally, three forms are reconstructed by one cognate in proto-Min. It is highly doubtful to regard those forms as a single stratum individually. Furthermore, the double rhymes, Xai and Tài, could be distinct in the Qieyun system but merged in most modern Chinese dialects. However, some southern dialects retain the distinction (refer to Cao et al. 2000, Wang 2004 and Wu 2005). How is the distinction of double rhymes expressed in proto-Min? It is worth examining those questions in depth.
The methodology of this paper is the comparative method. We would like to expand Min dialectal material and find more reliable cognates to reexamine Norman’s finals of Xai and Tài. From the perspective of historical development, proto-Min has several different phonological strata. After thoughtful and cautious analysis, those strata could be an important reference for the reconstruction of both Middle Chinese and Old Chinese. An important aim of this paper is to reconstruct the Jiangdong dialect, a southern Chinese dialect used in the Six Dynasties period, using proto-Min and related common dialect systems.
In conclusion: 1. both Xai and Tài could be reconstructed as two forms in the finals system of Proto-Min. In brief, *-əi and *-oi are for Xai; *-ɑi and *-ai are for Tài. 2. from a diachronic development viewpoint,the pattern *-oi: *-ai reveals the distinction of Xai and Tài, i.e. double rhyme, in the Six Dynasties Jiangdong dialect. 3. Relatedly, the pattern *-əi: *-ɑi could be traced to differences between the Zhi group （之部） and Jì group （祭部） in Old Chinese.