Four Classes of Readers

Readers may be divided into four classes: 1. Sponges, who absorb all they read, and retum it nearly in the same state, only a little dirtied. 2. Sand-glasses, who retain nothing, and are content to get through a book for the sake of getting through the time. 3. Strain-bags, who retain merely the dregs of what they read, and retum it nearly in the same state, only a little dirtied. 4. Mogul diamonds, equally rare and valuable, who profit by what they read, and enable others to profit by it also.

 Big History: A Summary of Evolution of Life on Earth

The first organisms, simple photosynthetic bacteria, appear in sediments about 3.5 billion years old, only about a billion years after the planet was formed. These single cells were all that occupied the Earth for the next two billion years, after which we see the first simple “eukaryotes”: organisms having true cells with nuclei and chromosomes. Then, around 600 million years ago, a whole gamut of relatively simple but multicelled organisms arise, including worms, jellyfish, and sponges....