such as that of Atypus, and the funnel nest of Cyrtauchenius elongatus, neither of which is furnished with a door.
Among the true trap-door nests, those of the cork type stand in a measure alone, being distinguished from all the others by their solid surface doors, composed of many layers of silk and earth; and we do not at present know of any intermediate forms linking the cork and wafer types together. But among the various nests which represent the wafer type the case is different, for here the types naturally fall into a progressive series, such as that represented in the diagrams (Pl. XIV., p. 193).
If we try to picture to ourselves the stages through which the most complicated wafer nest—namely, that of the double-door, branched, cavity type (Diagram G 1) may have passed in the course of its development from a simpler ancestral form, we should à priori expect to find precisely such structures as the Hyères double-door branched nest (Diagram F), and the single-door branched nest (Diagram D) forming successive halting-places in the advance from the primitive single-door, unbranched nest (Diagram C).
The double-door unbranched type may in like manner find its prototype in the same original single-door unbranched nest (C), which we may look upon as the parent idea, from which all these structures have been derived.
Bearing this in mind, and remembering that kinship between living creatures is not only revealed to us by likeness in structure and colour, but also by similarity in habits and instincts, it becomes of interest to trace any resemblance that may exist between
