Burrow and Emeneau (1961, p. xiii, n. 3) have observed that ‘Ta. and Ma. seem to have evidence for two phonemes [/n/, the dental and /ṉ/, the alveolar]a in PDr., but the matter is not yet clear’. This is mainly due to the non-availability of data about the distribution of these phonemes in those two languages and the allophonic distribution, if any, in other languages. With the help of increased material available now, an attempt is made in this paper to find out the history of the development of the two nasal phonemes in Ta. and Ma. and to establish their allophonic nature in PDr. Since definite information about the phonetic nature of the phoneme /n/ is not available for languages such as Kui, Parji, Nk. [Ch.] etc., this study is incomplete to some extent.