What is wanting, however, is not discussion, of which we have had enough, but demonstration, and demonstration is hard to come by, depending as it must upon careful and repeated experiment. If it were practicable, and I have no reason to know that it is not, to rear spiders from the egg away from the nest, and then to cause them to build in places where they should be perfectly at home and yet cut off from all communication with their kind, we might hope to learn whether they can construct the characteristic nests of their species without ever having seen one. Mr. Wallace[88] shows that there is some reason to doubt whether birds, which are so frequently said to build by instinct, would, under parallel circumstances, construct the nest proper to their kind; and he states that birds brought up from the egg in cages do not do so, nor do they even sing their parents' song without being taught. [Footnote 88: Chapters on Instinct and on the Philosophy of Birds' Nests, in his Contributions to the Theory of Natural Selection.] Of course we can scarcely compare birds and spiders together, but we should hesitate, in view of Mr. Wallace's expressed opinion as to the nest-building habits of the former, to assume that the latter are independent of teaching and personal experience. It may very possibly be so, but it has never been proved. I have endeavoured to gather together all the published records of the nests of spiders belonging to the sub-order _Territelariæ_, with a view, if possible, to trace out the geographical range of the several types of structure. I have, however, met with but a small amount of success, and even among the limited number of tolerably complete accounts of nests which I have been able to discover, several made no mention of the spider to which the nest belongs. Prof. Ausserer[89] has enumerated 215 species of _Territelariæ_ as having been found in the world at large, but of this large number ten only, as far as I have been able to learn, have been described in connexion with their nests, and eight of these belong to the Mediterranean region.[90] To these we may now add two more, namely, _Nemesia meridionalis_, with its branched double-door nest, and _N. Eleanora_ the builder of the unbranched double-door nest, thus making twelve in all. [Footnote 89: In his monograph of _Territelariæ_ quoted above.] [Footnote 90: I use this term in its widest sense, making it even include Morocco. A list of the species known to inhabit this region will be found in Appendix C.] Three of the twelve, however, _Atypus piceus_, _A. Blackwallii_, and _Nemesia cellicola_,[91] do not appear to build true trap-doors, but only a simple silk tube without any covering at the mouth. [Footnote 91: See Appendix A, p. 141.] The following tabular view will show to which of the four types of trap-door nest those of the remaining nine spiders belong, and their geographical distribution:-- TRAP-DOOR SPIDERS WHICH BUILD Nests of the cork type.