This paper is an enlarged version of the writer's lecture delivered at the 78th general meeting of the Linguistic Society of Japan. Two subjects are discussed: tonogenesis and ergative constructions in the TB languages. First, the sub-grouping of TB languages is mentioned briefly. With a number of examples the correspondence of cognate words in toneme dialects and tonemeless dialects within both the Chin and Tibetan groups is shown. The writer expresses his opinion concerning tonal development in the Choni dialect of Tibetan.
After considering the formation of toneme patterns in the disyllabic words of Lhasa Tibetan, the writer mentions the interesting phenomena of disyllabic words reduced to monosyllables evident in the Choni dialect in China, Dzongkha in Bhutan and Lhomi in Nepal.
In the second part he explains the ergative construction of Tibetan and discusses the opposition of ergative and non-ergative constructions. It is known that Tibetan originally had no passive construction as such, but in fact, when a passive meaning is called for, it is formed by the topicalization or focusization of the object of the sentence, as is clear in examples given which contrast with modern Chinese.
Finally, the writer points out what were probably ergative forms of Rawang of Northern Burma, Chiang in Ssu-Chuang and Moso in Yunnan; and he assumes the development of the ergative construction in Moso.