Just as in Christian countries there is a catechism of morals, which everyone knows by heart, but which no one considers it his duty to follow, or expects to see followed by others - so zoology also has its dogmas, which are just as generally professed as they are denied in practice.

Quoted in Ernst Heinrich Philipp August Haeckel, The History of Creation, Or, The Development of the Earth and Its Inhabitants by the Action of Natural Causes (Volume 1) (4th edition) (p. 51)