| series we have humble-bees, which use their old cocoons to hold honey, sometimes adding to them short tubes of wax, and likewise making separate and very irregular rounded cells of wax.  At the other end of the series we have the cells of the hive-bee, placed in a double layer: each cell, as is well known, is an hexagonal prism, with the basal edges of its six sides bevelled so as to 
 fit on to a pyramid, formed| fit 1860 1861 1866 1869 |  | join 1859 1872 | 
of three rhombs.  These rhombs have certain angles, and the three which form the pyramidal base of a single cell on one side of the 
 comb,| on to a pyramid, formed 1859 1860 1861 1866 1869 |  | an inverted pyramid, 1872 | 
enter into the composition of the bases of three adjoining cells on the opposite side.  In the series between the extreme perfection of the cells of the hive-bee and the simplicity of those of the 
 humble-bee,| comb, 1859 1860 1861 1866 1869 |  | comb 1872 | 
we have the cells of the Mexican Melipona domestica, carefully described and figured by Pierre Huber.  The Melipona itself is intermediate in structure between the hive and humble bee, but more nearly related to the 
 latter:| humble-bee, 1859 1860 1861 1866 |  | humble-bexe, 1869 |  | humble-bee 1872 | 
it forms a nearly regular waxen comb of cylindrical cells, in which the young are hatched, and, in addition, some large cells of wax for holding honey.  These latter cells are nearly spherical and of nearly equal sizes, and are aggregated into an irregular mass.  But the important point to 
 notice,| latter: 1859 1860 1861 1866 |  | latter; 1869 1872 | 
is| notice, 1859 1860 1861 1866 1869 |  | notice 1872 | 
that these 
 cells,| is 1859 1860 1861 1866 1869 |  | is, 1872 | 
are always made at that degree of nearness to each 
 other,| cells, 1866 |  | cells 1859 1860 1861 1869 1872 | 
that they would have intersected or broken into each 
 other,| other, 1859 1860 1861 1866 1869 |  | other 1872 | 
if the spheres had been completed; but this is never permitted, the bees building perfectly flat walls of wax between the spheres which thus tend to intersect. 
 Hence| other, 1859 1860 1861 1866 1869 |  | other 1872 | 
each cell consists of an outer spherical 
 portion,| Hence 1859 1860 1861 1866 1869 |  | Hence, 1872 | 
and of two, three, or more 
 perfectly| portion, 1866 1869 1872 |  | portion 1859 1860 1861 | 
flat surfaces, according as the cell adjoins two, three, or more other cells.  When one cell 
 rests on| perfectly 1859 1860 1861 1866 1869 |  | perfectly1872 | 
three other cells, which, from the spheres being nearly of the same size, is very frequently and necessarily the case, the three flat surfaces are united into| rests on 1866 1869 1872 |  | comes into contact with 1859 1860 1861 | 
 |