Evolution: The Modern Synthesis
Two of these papers were on the subject of sexual selection, an idea of Darwin's whose standing has been revived in recent times. Huxley thought that sexual selection was "...merely an aspect of natural selection". This rather grudging acceptance of sexual selection was influenced by his studies on the courtship of the Great Crested Grebe (and other birds that pair for life): the courtship takes place mostly after mate selection, not before.