Darwin did not use the term "variety of living things" as a specific scientific term. However, he used the term "variety" frequently in his work, specifically referring to variations within a species.

Here's how Darwin's ideas about variation related to his theory of evolution:

* Variation is the foundation of natural selection: Darwin recognized that individuals within a species exhibit variations in traits. These variations could be in size, color, behavior, or any other characteristic.

* Natural selection acts on variation: He proposed that some variations make individuals better suited to their environment, increasing their chances of survival and reproduction. Over time, these advantageous variations become more common in a population, while less advantageous ones decline.

* Evolution through descent with modification: This process of variation and natural selection leads to the gradual accumulation of changes within a species over generations, eventually resulting in new species.

So, while Darwin didn't use a specific term for the "variety of living things", his work heavily emphasized the importance of variation in explaining the diversity of life on Earth.