From the May 21, 1932, issue

GENES, ONCE HYPOTHETICAL, NOW SEEN AND PHOTOGRAPHED

Genes, the ultimate units in heredity, have been seen and photographed. So declares Dr. John Belling, biologist on the staff of the Carnegie Institution of Washington.

Genes have hitherto been dealt with as hypothetical entities by biologists, because no one has ever actually seen them. They were like the atoms and electrons that make up matter: Physicists treat them as actually existing things, though it is impossible to given them visual demonstration.