Light micrograph of the planktonic rotifer of the genus Keratella. Keratella rotifers have a strong armour into which the wheel organ is retracted in case of danger. The focus in this picture is on the inside of the animal. A red eye spot is visible below the rotifer. The yellow area underneath belongs to the animal's digestive system. At the end of the carapace on the right side of the picture you can see an egg with already partially developed daughter individual. Microscopic contrast method : Differential interference contrast. Magnification 420x at a print width of 10 cm.