The nests of the Mason-bee of the Walls are the more regular in structure and are easier to examine, because their base is wide open once it is separated from the supporting pebble; and it was these which supplied me with by far the greater part of my information. Those of the Mason-bee of the Sheds have to be chipped away with a hammer before one can inspect their cells, which are heaped up anyhow; and they do not lend themselves anything like so well to delicate investigations, as they suffer both from the shock and the ill-treatment. And now the thing is done: it remains certain that the Leucopsis' laying is exposed to very exceptional dangers. She can entrust the egg to sterile cells, without provisions fit to use; she can establish several in the same cell, though this cell contains nourishment for one only. Whether they proceed from a single individual returning several times, by inadvertence, to the same place, or are the work of different individuals unaware of the previous borings, those multiple layings are very frequent, almost as much so as the normal layings. The largest which I have noticed consisted of five eggs, but we have no authority for looking upon this number as an outside limit. Who could say, when the perforators are numerous, to what lengths this accumulation can go? I will set forth on some future occasion how the ration of one egg remains in reality the ration of one egg, despite the multiplicity of banqueters. I will end by describing the egg, which is a white, opaque object, shaped like a much-elongated oval. One of the ends is lengthened out into a neck or pedicle, which is as long as the egg proper. This neck is somewhat wrinkled, sinuous and as a rule considerably curved. The whole thing is not at all unlike certain gourds with an elongated paunch and a snake-like neck. The total length, pedicle and all, is about 3 millimetres. (About one-eighth of an inch.--Translator's Note.) It is needless to say, after recognizing the grub's manner of feeding, that this egg is not laid inside the fostering larva. Yet, before I knew the habits of the Leucopsis, I would readily have believed that every Hymenopteron armed with a long probe inserts her eggs into the victim's sides, as the Ichneumon-flies do to the Caterpillars. I mention this for the benefit of any who may be under the same erroneous impression.