The great trap-door group therefore comprises spiders which differ widely in respect of their dwelling places. Some construct no nest at all or only an irregular web, and live under stones; others, like _Theraphosa Blondii_, make a simple cylindrical tunnel, or, like those just described, a tube having a prolonged, uncovered, funnel-shaped mouth: others again, belonging to the genus _Atypus_, form the curious and as yet imperfectly-understood nests with a silken tubular lining, part of which hangs down outside; while on the highest rung of the architectural ladder, stand the builders of the veritable trap-door nests. It seems quite possible that, when we know more of the structures made by _Territelariæ_ generally in various parts of the world, we shall find that nests of various degrees of complexity and perfection of structure exist, bridging over the gulf between the barbarous dwellers under stones and the highly civilized inhabitants of the branched wafer and cork nests. Indeed, thanks to recent discoveries, I am already able to do something of this kind for one small group of spiders, namely, for that of the European _Nemesias_ having nests with wafer doors. [Illustration: _Plate XIV._] I hope to make this plain by reference to the diagrams on Plate XIV., where the figures C, D, E, F, and G represent on a reduced scale five types of wafer nest constructed by as many distinct spiders, and where a gradation may readily be traced between the simplest type at C and the most complicated at G; but we shall speak more fully of this matter by-and-by. In these diagrams I have placed that representing the nest of _Atypus_ on the extreme left (A);[130] next to this stands that of a nest of the cork type (B), a type which must be carefully distinguished from all the rest. It must not be supposed that the solid cork door (so called from its resemblance to a short cork closing the neck of a bottle), is nothing more than a thicker edition of the wafer door; it is not so, but, on the contrary, possesses a very characteristic structure of its own, being composed of many layers of silk, each furnished with a sloping rim of earth, while the wafer door consists of but a single layer of silk. [Footnote 130: These types may be briefly enumerated as follows: A, nest of _Atypus_. B, cork nest, and B, 1, layers of silk and earth forming the door of the cork nest. C, single-door, unbranched wafer nest. D, single door, branched wafer nest. E, double-door, unbranched wafer nest, and E, 1, lower door of the same. F, the Hyères double-door branched wafer nest, and F, 1, lower door of the same. G, double-door branched cavity wafer nest, as seen in the oldest and largest specimens, and G, 1, the same in the younger specimens. G, 2, the lower door of this nest, being of the same form in young and old nests. ]