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 and .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 in diameter.

(.195 to .234 inch .-- Translator's Note.) Each of the two parts of the double-galleried tunnel, one narrow and one wide, measures at most a decimetre in length.