Euglena, the microscopic, one-celled organism, belongs to the Protista kingdom and the phylum Euglenophyta. Most live in quiet fresh water streams and ponds. Also, some Euglena are likely to develop within a polluted, fertilized body of water. The Euglena is rather common in warm seasons, where there is an abundance of rich organic waste. The Euglena is generally rotund. It is asymmetrical and can be flattened. Of the 150 species of Euglena, most tend to be green because of the chlorophyll, which creates the production of food through photosynthesis. However, some species can be bright red, due to a pigment called the astaxanthin. Because Euglena carried out photosynthesis but was mobile, many early scientists were quite baffled: It had carried the characteristics of both a plant and an animal (considering the fact that most plant are not mobile and most animals are not able to carry out photosynthesis). Since they wanted to sub-divide every living thing into either plants or animals, Euglena was a rather " mysterious" form of an organism. Euglena's size ranges from 1/1000 to 1/100 of an inch, or 0.025 CM to 0.254 CM. Euglena moves by a flagellum, which is located on the front end of the euglena. Like many other Euglenoids, the Euglena has only one flagellum. It is similar to a long whip-like structure that propels the cell throughout the water. For an example, the flagellum of a euglena would function like the propeller on an airplane. The flagellum would curl in order to pull the cell through the water, just as the propeller would spin on the air. The flagellum is attached to an inner pocket called the reservoir. Another crucial body structure is the eyespot, the pigmented organelle. The euglena contains the eyespot at the anterior (front) end of its body. The eyespot serves as a light shield. The eyespot selects a certain direction to strike the light detector, the bulge near the base of the flagellum.