The foamy mass consists chiefly of air imprisoned in minute bubbles. This air, which gives the nest a volume very much greater than that of the abdomen of the Mantis, evidently does not issue from the insect although the foam appears at the orifice of the genital organs; it is borrowed from the atmosphere. The Mantis builds more especially with air, which is eminently adapted to protect the nest against changes of temperature. She emits a glutinous substance like the liquid secretion of silk-worms, and with this composition, mixed instantaneously with the outer air, she produces the foam of which the nest is constructed. She whips the secretion as we whip white of egg, in order to make it rise and stiffen. The extremity of the abdomen opens in a long cleft, forming two lateral ladles which open and shut with a rapid, incessant movement, beating the viscous liquid and converting it into foam as it is secreted. Beside the two oscillating ladles we see the internal organs rising and falling, protruding and retreating like a piston-rod, but it is impossible to observe the precise nature of their action, bathed as they are in the opaque blob of foam. The end of the abdomen, continually palpitating, rapidly closing and opening its valves, oscillates right and left like a pendulum. From each of these oscillations results a layer of eggs in the interior, and a transversal crevice on the exterior. As it advances in the arc described, suddenly, and at frequent intervals, it plunges deeper into the foam, as though burying something at the bottom of the frothy mass. Each time it does so an egg is doubtless deposited; but the operation is so rapid, and takes place under conditions so unfavourable for observation, that I have never once been enabled to see the oviduct at work. I can only judge of the advent of the eggs by the movements of the end of the abdomen, which is immersed more deeply with a sudden plunging movement. At the same time the viscous composition is emitted in intermittent waves, and is beaten into a foam by the terminal valves. The foam thus obtained spreads itself over the sides and at the base of the layer of eggs, and projects through the meshes of the wire gauze as a result of the pressure of the abdomen. Thus the spongy envelope is progressively created as the ovaries are gradually emptied. I imagine, although I cannot speak as the result of direct observation, that for the central core, where the eggs are surrounded by a material more homogeneous than that of the outer shell, the Mantis must employ her secretion as it emerges, without beating it into a foam. The layer of eggs once deposited, the two valves would produce the foam required to envelop the eggs. It is extremely difficult, however, to guess what occurs beneath the veil of foam-like secretion.