燃素，热素原来假设的在所有燃烧物质中挥发性的一种物质成分，在燃烧中作为火焰而被释放出来 A hypothetical substance formerly thought to be a volatile constituent of all combustible substances released as flame in combustion.
物种原形演化成后来各物种的真实存在的或假设的有机物 The actual or hypothetical organism or stock from which later kinds evolved.
