This collection of stories, told by some biologists whose work and careers have been strongly influenced by Max Delbrück (or, in the case of a few, had influenced him), is dedicated to him on his 60th birthday.

The reader will probably wonder why there should be a Festschrift in honor of a man still in his prime. Why not wait until he has joined the ranks of senior citizens whom custom favors as subjects for such commemoration ? The answer lies in the exponentially increasing growth rate of science which has now reached such a pitch that one lifetime encompasses many scientific eras. Thus the singular contribution that Delbrück made some 25 years ago already seems to lie in a past so distant that the circumstances attending it are no longer easy to reconstruct. In another ten or twenty years, they might have been beyond recall. Besides paying homage to Delbrück as a prime mover and arbiter of nascent molecular biology, this book is an attempt therefore to write a history of a bygone age and put on record the network of interactions, folklore, and method of operation of the Phage Group that had Delbrück as its focal point.

Only one of the articles was not expressly written for the book, namely (and understandably) Delbriick's own 1949 essay, "A Physicist Looks at Biology." In this essay, a lecture given at the thousandth meeting of the Connecticut Academy of Arts and Sciences, Delbrück described the spirit of the 1930's and 1940's that moved many of the creators of molecular biology before the dénouement brought by the discovery of the structure of DNA in 1953. We are very grateful to the Connecticut Academy for permission to reprint it.

The reader will notice that not only the names of a few particular people but also the names of two scientific institutions keep recurring in the following pages - the California Institute of Technology and the Cold Spring Harbor Laboratory. These two places, at opposite ends of the American continent, were the Mecca and Medina of the Phage Group to which the faithful made their periodic hadj (though later the Institut Pasteur and the Cambridge Molecular Biology Laboratory were to cut into the pilgrim trade). Caltech, though not large by the standards ofAmerican universities, is a powerful and world-famous institution and was already renowned for its galaxy of outstanding physicists, chemists and biologists when Delbrück came there in the late 1930's. It was therefore a natural breeding ground for the ideas that were later to give the keys to the physical basis of heredity. But why Cold Spring Harbor, a small station of meager resources on the shores of Long Island Sound, should have played such an important role may not be as immediately obvious. It is fitting, therefore, to point out that this became possible through the imagination and enterprise of Milislav Demerec, who was Director at Cold Spring Harbor from 1941 until his retirement in 1960. Demerec was a prominent Drosophila geneticist when, in the early 1940's, he realized that bacteria and their viruses were likely to become the materials of choice for basic studies in genetics. He then not only moved his own work from classical to molecular genetics but also managed, at the same time, to conjure up the wherewithal for others to do likewise. For this the many contributors to this book whose scientific evolution took a decisive turn on a visit to Cold Spring Harbor are greatly in Dr. Demerec's debt. It seems singularly appropriate therefore that this book is being published by the laboratory he brought into prominence.

Although the essays presented here cover a period of some thirty years, most of them describe work done in the twenty-one years that have passed since Delbrück gave the first Phage Course at Cold Spring Harbor in 1945. Thus the book may be thought to commemorate also the coming of age of that annual course, which will celebrate its twenty-first birthday this summer.

JOHN CAIRNS
GUNTHER S. STENT
JAMES D. WATSON
May, 1966

Table of Contents

Preface - John Cairns, Gunther S. Stent, James D. Watson

I. ORIGINS OF MOLECULAR BIOLOGY

Introduction: Waiting for the Paradox - Gunther S. Stent
A Physicist Looks at Biology - Max Delbrück
Biochemical Genetics: Some Recollection - George W. Beadle
The Target Theory - K. G. Zimmer
High Energy Phosphate Bonds : Optional or Obligatory ? - Herman M. Kalckar

II. THE PHAGE RENAISSANCE

Bacteriophage: One-Step Growth - Emory L. Ellis
Electron Microscopy of Phages - Thomas F. Anderson
The Eclipse in the Bacteriophage Life Cycle - A. H. Doermann
The Prophage and I - Andre Lwoff
The Injection of DNA into Cells by Phage - A. D. Hershey
Transfer of Parental Material to Progeny - Lloyd M. Kozloff
Electron Microscopy of Developing Bacteriophage - Edward Kellenberger

III. PHAGE GENETICS

Phenotypic Mixing- Aaron Novick
Mating Theory - N. Visconti
On the Physical Basis of Genetic Structure in Bacteriophage -A. D. Kaiser
Adventures in the rII Region - Seymour Benzer
Conditional Lethals- R. S. Edgar

IV. BACTERIAL GENETICS

Mutations of Bacteria and of Bacteriophage- S. E. Luria
Gene, Transforming Principle, and DNA - Rollin D. Hotchkiss
Sexual DifFerentiation in Bacteria - William Hayes
Bacterial Conjugation - Elie L. Wollman
Story and Structure of the lambda Transducing Phage - J. Weigle

V. DNA

Growing Up in the Phage Group - J. D. Watson
Demonstration of the Semiconservative Mode of DNA Duplication - Matthew Meselson and Franklin W. Stahl
The Autoradiography of DANN - John Cairns
Multum in Parvo - Robert L. Sinsheimer
The Relation between Nuclear and Cellular Division in Escherichia coli - Ole Maaloe

VI. RAMIFICATIONS OF MOLECULAR BIOLOGY

The Mammalian Cell - T. T. Puck
The Plaque Technique and the Development of Quantitative Animal Virology - Renato Dulbecco
Quantitative Tumor Virology - H. Rubin
The Natural Selection Theory of Antibody Formation; Ten Years Later – Niels Jerne
Cybernetics of the Insect Optomotor Response - Werner E. Reichardt
Terminal Redundancy, or All's Well that Ends Well - George Streisinger