Petri dish Petri dish A Petri dish (sometimes spelled "Petrie Dish" and alternatively known as a Petri plate or cell-culture dish), named after the German bacteriologist Julius Richard Petri, is a shallow cylindrical glass or plastic lidded dish that biologists use to culture cellssuch as bacteriaor small mosses. Modern Petri dishes usually feature rings and/or slots on their lids and bases so that when stacked, they are less prone to sliding off one another. Multiple dishes can also be incorporated into one plastic container to create a "multi-well plate". While glass Petri dishes may be reused after sterilization (via an autoclave at
Evolution of the eye eye resemble the previous layout. Vertebrate lenses are composed of adapted epithelial cells which have high concentrations of the protein crystallin. These crystallins belong to two major families, the α-crystallins and the βγ-crystallins. Both were categories of proteins originally used for other functions in organisms, but eventually were adapted for the sole purpose of vision in animal eyes. In the embryo, the lens is living tissue, but the cellular machinery is not transparent so must be removed before the organism can see. Removing the machinery means the lens is composed of dead cells, packed with crystallins. These crystallins are special