It appears, then, that the Mesê of the Greek standard System had the functions of a key-note in that System. In other words, the music was in the _mode_ (using that term in the modern sense) represented by the octave _a-a_ of the natural key--the Hypo-dorian or Common Species. We do not indeed know how the predominant character of the Mesê was shown--whether, for example, the melody ended on the Mesê. The supposed evidence for an ending on the Hypatê has been shown to be insufficient. But we may at least hold that as far as the Mesê was a key-note, so far the Greek scale was that of the modern Minor mode (descending). The only way of escape from this conclusion is to deny that the Mesê of _Probl._ xix. 20 was the note which we have understood by the term--the Mesê of the standard System. This, as we shall presently see, is the plea to which Westphal has recourse. § 21. _The Species of a Scale._ The object of the preceding discussion has been to make it clear that the theory of a system of modes--in the modern sense of the word--finds no support from the earlier authorities on Greek music. There is, however, evidence to show that Aristoxenus, and perhaps other writers of the time, gave much thought to the varieties to be obtained by taking the intervals of a scale in different order. These varieties they spoke of as the _forms_ or _species_ ([Greek: schêmata, eidê]) of the interval which measured the compass of the scale in question. Thus, the interval of the Octave ([Greek: dia pasôn]) is divided into seven intervals, and these are, in the Diatonic genus, five tones and two semitones, in the Enharmonic two ditones, four quarter-tones, and a tone. As we shall presently see in detail, there are seven species of the Octave in each genus. That is to say, there are seven admissible octachord scales ([Greek: systêmata emmelê]), differing only in the succession of the intervals which compose them. Further, there is evidence which goes to connect the seven species of the Octave with the Modes or [Greek: harmoniai]. In some writers these species are described under names which are familiar to us in their application to the modes. A certain succession of intervals is called the Dorian species of the Octave, another succession is called the Phrygian species, and so on for the Lydian, Mixo-lydian, Hypo-dorian, Hypo-phrygian, and Hypo-lydian. It seems natural to conclude that the species or successions of intervals so named were characteristic in some way of the modes which bore the same names, consequently that the modes were not keys, but modes in the modern sense of the term.