I have argued elsewhere (Connell, 1997) that the fricative vowels of Len may well reflect a Grassfields substratum in Len.
 It is not entirely clear what Meinhof considered to be the phonetic nature of Ur Bantu and . He refers to these two vowels as being `close' as opposed to `open' and , but at one point describes the difference between them as front ( and ) as opposed to back ( and ), and later, as mentioned below, diagrams them all at the same degree of height. He did consider and to have a quality of tenseness not associated with and , which presumably contributed to the friction, or fricating effect.
 Assuming the feature [+/-ATR] is intended here to have any phonetic content, this notion for PB appears to be problematic. First, there is no evidence from Bantu languages today to substantiate an [+/-ATR] distinction for these vowels, at least in the sense that this feature is applied to langauges such as Igbo and Akan. Second, it strongly suggests that [+ATR], i.e. tongue root retraction, was the phonetic `trigger' for spirantization, a scenario difficult to imagine.