I can no longer claim to be an expert on superconductivity and superfluidity: I have been unable to keep up with recent advances in theory and experiment and they are numerous and important. But I was somewhat active in this field in the thirties and it so happens that this was a rather important period in the history of the subject. And so, although I am unable to do justice to the subject in its entirety, I may at least be able to explain some features of its development.