Next I have plotted, on the same diagram, and in relation to the same scales of angles, the corresponding lengths of the two partitions, viz. _RS_ and _MP_, their lengths being expressed (on the right-hand side of the diagram) in relation to the radius of the circle (_a_), that is to say the side wall, _OA_, of our cell. The limiting values here are (1), _C_, _C′_, where the angle of arc is 90°, and where, as we have already seen, the two partition-walls have the relative magnitudes of _MP_ : _RS_ = 0·875 : 1·111; (2) the point _D_, where _RS_ equals unity, that is to say where the periclinal partition has the same length as a radial one; this occurs when α is rather under 82° (cf. the points _D_, _D′_); (3) the point _E_, where _RS_ and _MP_ intersect; that is to say the point at which the two partitions, periclinal and anticlinal, are of the same magnitude; this is the case, according to our diagram, when the angle of arc is just over 62½°. We see from this, then, that what we have called an anticlinal partition, as _MP_, is only likely to occur in a triangular or prismatic cell whose angle of arc lies between 90° and 62½°. In all narrower or more tapering cells, the periclinal partition will be of less area, and will therefore be more and more likely to occur. The case (_F_) where the angle α is just 60° is of some interest. Here, owing to the curvature of the peripheral border, and the consequent fact that the peripheral angles are somewhat greater than the apical angle α, the periclinal partition has a very slight and almost imperceptible advantage over the anticlinal, the relative proportions being about as _MP_ : _RS_ = 0·73 : 0·72. But if the equilateral triangle be a plane spherical triangle, i.e. a plane triangle bounded by circular arcs, then we see that there is no longer any distinction at all between our two partitions; _MP_ and _RS_ are now identical. On the same diagram, I have inserted the curve for values of {367} cosec θ − cot θ = _OM_, that is to say the distances from the centre, along the side of the cell, of the starting-point (_M_) of the anticlinal partition. The point _C″_ represents its position in the case of a quadrant, and shews it to be (as we have already said) about 3/10 of the length of the radius from the centre. If, on the other hand, our cell be an equilateral triangle, then we have to read off the point on this curve corresponding to α = 60°, and we find it at the point _F‴_ (vertically under _F_), which tells us that the partition now starts 4·5/10, or nearly halfway, along the radial wall. ――――――――――