ther. Moreover,
I have scattered in front of either hive a few handfuls of empty
Snail-shells, specially chosen for the object which I have in view.
Reasons which I will explain later led me to prefer the shells of Helix
caespitum. Each of the shells, as and when stocked, received the date
of the laying and the alphabetical sign corresponding with the Osmia to
whom it belonged. In this way, I spent five or six weeks in continual
observation. To succeed in an enquiry, the first and foremost condition
is patience. This condition I fulfilled; and it was rewarded with the
success which I was justified in expecting.

The tubes employed are of two kinds. The first, which are cylindrical
and of the same width throughout, will be of use for confirming the
facts observed in the first year of my experiments in indoor rearing.
The others, the majority, consist of two cylinders which are of very
different diameters, set end to end. The front cylinder, the one which
projects a little way outside the hive and forms the entrance-hole,
varies in width between 8 and 12 millimetres. (Between.312 to .468
inch.--Translator's Note.) The second, the back one, contained
entirely within my packing-case, is closed at its far end and is 5 to 6
millimetres (.195 to.234 inch.--Translator's Note.) in diameter. Each of
the two parts of the double-galleried tunnel, one narrow and one wide,
measures at most a decimetre (3.9 inches.--Translator's Note.) in
length. I thought it advisable to have these short tubes, as the Osmia
is thus compelled to select different lodgings, each of them being
insufficient in itself to accommodate the total laying. In this way I
shall obtain a greater variety in the distribution of the sexes. Lastly,
at the mouth of each tube, which projects slightly outside the case,
there is a little paper tongue, forming a sort of perch on which the
Osmia alights on her arrival and giving easy access to the house. With
these facilities, the swarm colonized fifty-two double-galleried tubes,
thirty-seven cylindrical tubes, seventy-eight Snail-shells and a few old
nests of the Mason-bee of the Shrubs. From this rich mine of material I
will take what I want to prove my case.

Every series, even when incomplete, begins with females and ends with
males. To this rule I have not yet found an exception, at least in
galleries of normal diameter. In each new abode, the mother busies
herself first of all with the more important sex. Bearing this