By Tuesday evening the track had been cleared to the three snowbound engines, and the following day, under their own steam, they were moved away; the business of relighting their fires and raising steam in such conditions is better imagined than described.

It is likely that the long evolutionary trajectory of Mycoplasma went from a reductive autotroph to oxidative heterotroph to a cell-wall–defective degenerate parasite. This evolutionary trajectory assumes the simplicity to complexity route of biogenesis, a point of view that is not universally accepted.

I’ll call your 300, and raise to 600!

We give a structural description of the finite subsets A of an arbitrary group G which obey the polynomial growth condition for some bounded d and sufficiently large n, showing that such sets are controlled by (a bounded number of translates of) a coset nilprogression in a certain precise sense.