IN a recent communication1, Prof. C. H. Waddington protests against the increasing use of the name `molecular biology' for a large and ever-growing field to which, he argues, it does not apply, and suggests confining it to more restricted topics for which in any event a better name would be `ultra-structural biology'. Since, as I believe, I was responsible for first propagating the name `molecular biology', and its widespread adoption seems to date particularly from my 1950 Harvey Lecture ``Adventures in Molecular Biology''2, it may be worth while stating again what I personally had in mind. In that lecture I said that molecular biology, as I envisaged it, ``implies not so much a technique as an approach, an approach from the viewpoint of the so-called basic sciences with the leading idea of searching below the large-scale manifestations of classical biology for the corresponding molecular plan. It is concerned particularly with the forms of biological molecules, and with the evolution, exploitation and ramification of those forms in the ascent to higher and higher levels of organisation. Molecular biology is predominantly three-dimensional and structural-which does not mean, however, that it is merely a refinement of morphology. It must at the same time inquire into genesis and function''.