Your view is new to me, and has only to be suggested for its probability to be recognised.² I presume that of course you would thus account only in part for the retention of a tail and for its modification. Your view does not preclude the conjoint use of the tail for other service, as for gliding through the air when flattened, as in the squirrel, or as a signal to beasts of prey, in accordance with Mr. Betts’s ingenious suggestion in his Nicaraguan travels, with respect to the great bushy and conspicuously-coloured tail of the skunks.³ I wish we knew the use of the extraordinary tail of the yak, which inhabits such cold regions, whether it serves solely as a fly-flapper.⁴ If poor Dr. Falconer⁵ had been alive he could have told us.