Quote of the Week: Spirals

Of true organic spirals we have no lack. We think at once of horns of ruminants, and of still more exquisitely beautiful molluscan shells ... Closey related spirals may be traced in the florets of a sunflower; a true spiral, though not, by the way, so easy of investigation, is seen in the outline of a clodiform leaf; and yet again, we can recognise typical though transitory spirals in a lock of hair, in a staple of wool, in the coil of an elephant's trunk, in the 'circling spirals' of a snake, in the coils of a cuttle-fish's arm, or of a monkey's or a chameleon's tail.

Among such forms as these, and the many others which we might easily add to them, it is obvious that we have to do with things which, though mathematically similar, are biologically speaking fundamentally different; and not only are they biologically remote, but they are also physically different, in regard to the causes to which they are severally due.

Sir D'Arcy Thompson, On Growth and Form