THE HIVE BEE. 39 
assume the hexagonal form by equal pressure in all direc- 
tions. Every one knows that cylinders made of a yielding 
substance always become hexagonal if pressed together, 
and a similar process was supposed to cause the hexagonal 
shape of the Bee-cell. 
There is another theory, which I believe to be entirely 
original, which is suggested by the well-known mathe- 
matician and crystallographer above-mentioned. Mr. 
Mitchell writes to me as follows: “It may not be out of 
place to remark that the Bee-cell forms a mould, as it were, 
of the natural form of a crystal. There is in nature a 
great variety of crystals, hexagonal prisms terminated by 
three planes, like the Bee-cell. These have many different 
angles. But there is one form, called the rhombic dodeca- 
hedron (see fig. 6), very frequently found in natural crystals 
of the garnet, which has precisely the same angles as the 
Bee-cell. 
“ Certain crystals split naturally into planes precisely 
like the lozenges which have already been described in 
giving the key to the structure of the Bee-cell. May it 
not, therefore, be possible that wax, which is a crystallis- 
able substance, cleaves in this particular direction, and does 
the Bee use this property in forming its cell? Though 
this vague conjecture should prove to be true, we shall 
not less admire the marvellous instinct which combines 
this fact with the structure of the cell.” 
It would, of course, be easy to fill many pages with the 
account of the Hive Bee and its habits; but as this work 
is restricted to the habitations of animals, we can only look 
upon the Bee as a maker of social habitations. It will, 
however, be necessary to mention the material of which 
the comb is made. 
The other hymenoptera obtain their materials from 
external sources. The hornet and wasp have recourse to 
