I Shall not attempt to repeat or even to summarize the excellent discussion of glottochronology by Dr D. H. Hymes (Current Anthropology, I, I, January 1960), but shall to some extent base my remarks on it. It seems to me that glottochronology is one method of analysis among many. It sheds a certain light of its own which is most useful when related to other kinds of study. The method of common innovations, for example, gives a much more precise picture of the genetic relations of a set of languages, and it does not depend on so many controversial assumptions. But the chronology which it gives is always a relative one. Furthermore, it depends for its success on quite deep studies of the languages in question, since it is always hazardous to say that a particular form or construction is not present in a language. Further study may often reveal it. It is, of course, also true of glottochronology that it depends for its full success on the deep study of the languages under consideration and of their cognate interrelations. It appears that we shall have to wait quite some time for those conditions to be satisfied in African studies, and field workers have had to go ahead and use these methods as best they can in order to make some kind of sense out of the vast mass of data before them. It seems to me that this is legitimate if all the conclusions of such exploratory ventures are firmly held to be subject to change without notice. We can at least get some idea of the time depths with which we are dealing. Language relationships which are recent enough to be of historical interest are fairly easy to handle even with crude methods. It is with respect to the older relationships that technique is stretched to its uttermost limits. Even here glottochronology can establish a ground against which recent borrrowings, containing the traces left by historical process, can be more readily distinguished.