The genus is unique in its ability to traverse the heatless and airless interstellar void in full corporeal form, and some of its variants cannot do this without mechanical aid or curious surgical transpositions. Only a few species have the ether-resisting wings characteristic of the Vermont variety. Those inhabiting certain remote peaks in the Old World were brought in other ways. Their external resemblance to animal life, and to the sort of structure we understand as material, is a matter of parallel evolution rather than of close kinship. Their brain-capacity exceeds that of any other surviving life-form, although the winged types of our hill country are by no means the most highly developed. Telepathy is their usual means of discourse, though we have rudimentary vocal organs which, after a slight operation (for surgery is an incredibly expert and everyday thing among them), can roughly duplicate the speech of such types of organism as still use speech.