building perfectly flat walls of wax between the spheres which thus tend to intersect. Hence, each cell consists of an outer spherical portion, and of two, three, or more, perfectly flat surfaces, according as the cell adjoins two, three, or more cells; and when one cell rests on three others, as from the spheres being nearly of the same size is very frequently and necessarily the case, the three flat surfaces are united into a pyramid rudely resembling the three-sided pyramidal base of the hive bee's cell, and necessarily enter, like the three rhombs of the latter, into the construction of three adjoining cells.' Reflecting on these remarkable gradations, it occurred to Mr. Darwin that if the melipona were to make its spheres of precisely equal sizes, and to arrange them symmetrically in double layers, and were further so to dispose them as that the centre of each should be at the distance of radius x [mathematical symbol 'square root']2 or radius x 1.41421 from the centres of the six surrounding spheres in the same layer, and at the same distance from the centres of the adjoining spheres in the other and parallel layer--then 'if planes of intersection between the several spheres on both layers were formed, there would result a double layer of hexagonal prisms united together by pyramidal bases formed of three rhombs; and the rhombs and the sides of the hexagonal prisms would have every angle identically the same with the best measurements that have been made of the cells of the hive bee.' Then, submitting this view to Professor Miller of Cambridge, he had the gratification of being assured by that distinguished geometer that it was strictly correct. Certainly a very happy example of an ingenious conjecture verified by a species of demonstration hardly inferior to the experimental. Certainly a very valuable testimony to the soundness of all the main and really essential principles of Darwinism. Good cause, certainly, is hereby shown for believing that the cell-making faculty of the hive bee may be nothing more than the aggregate of many minute and successive improvements upon that of the melipona, and this, again, than a similar aggregate of improvements on that of the humble bee; and for believing further that hive bee and melipona may both be either descendants from the humble bee, or joint-descendants with it from some still earlier common progenitor. In order to believe this it suffices to believe that a bee which at one period made, like the humble bee, cells very unequally sized and irregularly rounded, came gradually, in the course of time, to make them as nearly equal in size and as nearly spherical as those of the melipona; and subsequently, during a further lapse of time, came to arrange them at the same distances from each other, and in double layers like those of the humble bee. To assume thus much requires no inordinate stretch of faith; and thus much being assumed, it is seen at