Research workers in agriculture were, as usual, ahead of the game. Diluents such as blood serum, sugars, gelatin and buffers were tried (Mann 1954) but Phillip's and Lardy's (1940) discovery of the value of hens' egg yolk plus buffers for extending the viability of mammalian and avian sperm proved to be a minor breakthrough. Fish seemed to present different problems because fertilization was usually external after the eggs and sperm had been released into the surrounding medium.