The element shown in figure 10, _a-e_ is a case in point. In _a_ and _b_ we have what may be called the normal or regular forms of this element. In _c_, however, the upper arm has been omitted for the sake of symmetry in a composite glyph, while in _d_ the lower arm has been left out for want of space. Finally in _e_ both arms have disappeared and the element is reduced to the sign (), which we may conclude, therefore, is the essential characteristic of this glyph, particularly since there is no regularity in the treatment of the arms in the normal forms. This suggests another point of the utmost importance, namely, the determination of the essential elements of Maya glyphs. The importance of this point lies in the fact that great license was permitted in the treatment of accessory elements so long as the essential element or elements of a glyph could readily be recognized as such. In this way may be explained the use of the so-called "head" variants, in which the outline of the glyph was represented as a human or a grotesque head modified in some way by the essential element of the intended form. The first step in the development of head variants is seen in figure 11, _a_, _b_, in which the entire glyph _a_ is used as a headdress in glyph _b_, the meaning of the two forms remaining identical. The next step is shown in the same figure, _c_ and _d_, in which the outline of the entire glyph _c_ has been changed to form the grotesque head _d_, though in both glyphs the essential elements are the same. A further development was to apply the essential element () of _e_ to the head in _f_, giving rise to a head variant, the meaning of which suffered no corresponding change. The element (+) in figure 11, _g_, has been reduced in size in _h_, though the other two essential elements remain unchanged. A final step appears in _i_ and _j_, where in _j_ the position of one of the two essential elements of _i_ () and the form of the other (++) have been changed. These variants {25} are puzzling enough when the essential characteristics and meaning of a glyph have been determined, but when both are unknown the problem is indeed knotty. For example, it would seem as a logical deduction from the foregoing examples, that _l_ of figure 11 is a "head" variant of _k_; and similarly _n_ might be a "head" variant of _m_, but here we are treading on uncertain ground, as the meanings of these forms are unknown.