FlagellumA long whip at the front end. It beats to move the cell through the water. A second, short flagellum never leaves the reservoir.
Eyespot (stigma)A patch of pigment granules near the front. As the cell turns, it shades the photoreceptor, which helps the cell find the light.
ChloroplastsThey make food for the cell from light. Each holds chlorophyll, as the chloroplasts of a plant do.
NucleusOne nucleus lies near the middle of the cell. It divides first when the cell splits in two.
Contractile vacuoleA round sac that collects excess water. It empties into the reservoir, and the water leaves the cell from there.
PellicleA flexible coat of protein strips, not a cell wall. The strips slide past one another, so the cell can change its shape.
The front end 2
ReservoirA pocket in the cell's front. Both flagella rise from its floor, and the contractile vacuole empties into it.
PhotoreceptorA swelling near the base of the long flagellum. It is the part that detects light, and it is also called the paraflagellar body.
The rest of the cell 1
Paramylon granulesGrains of stored food. Paramylon is a carbohydrate like starch, built from the sugar the chloroplasts make.
How this list was compiled: Every name was checked on 2026-10-01 and kept only where two independent sources use it for Euglena. (1) Wikipedia, text only: Euglena, https://en.wikipedia.org/wiki/Euglena . (2) R. W. Hegner, College Zoology (1912), the section on Euglena viridis, public domain, https://archive.org/details/collegezoology00hegn . (3) George M. Briggs, Inanimate Life, the chapter on Euglena, an open college botany textbook, https://milnepublishing.geneseo.edu/botany/chapter/euglena/ . (4) Two journal abstracts and one open-access paper on how Euglena finds light, read through Europe PMC: https://europepmc.org/article/MED/31630463 , https://europepmc.org/article/MED/28429324 and https://europepmc.org/article/PMC/PMC8911436 . Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
A fill in the blank diagram of a euglena cell, drawn front end up: a whip at the top, a pocket under it, and discs, capsules and one large round body lower down. Nine label lines each want a name.
Read the full guide
Word bank for the nine blanks
Flagellum, eyespot, chloroplasts, nucleus, contractile vacuole, pellicle, reservoir, photoreceptor, paramylon granules. A class may say stigma for the eyespot and paraflagellar body for the photoreceptor. An old zoology book says cuticle for the pellicle, chromatophores for the chloroplasts and paramylum for paramylon.
Three pairs that get swapped
Eyespot and photoreceptor: the spotted oval beside the neck of the pocket is the eyespot, and the dark bead on the whip inside that neck is the photoreceptor. Reservoir and contractile vacuole: the pocket the whip rises from is the reservoir, and the sac ringed with smaller ones that touches it is the contractile vacuole. Chloroplasts and paramylon granules: the oval discs are chloroplasts, and the small capsules between them are the granules.
The three easy blanks: the whip is the flagellum, the striped outer band the pellicle, and the large round body the nucleus.
The short second whip inside the pocket, the two dots both whips grow from and the dark center of the nucleus take no name.
Questions and answers
How many flagella does a euglena have?
Two. One is long and leaves the cell, and it is the one the sheet asks for. The other is very short and never leaves the reservoir. The long one can be seen with a light microscope.
Where does euglena live?
In fresh water and in salt water. It is often abundant in quiet inland waters, where it can bloom in numbers that color the surface of a pond or a ditch green.
How does a euglena reproduce?
By binary fission, one cell dividing into two. The nucleus divides first. The cell then splits lengthwise, starting at the front end, until the two halves are apart.
What does the word euglena mean?
The name was built in 1830 from two Greek roots, eu for good and glene for eyeball. It points at the eyespot, which a new kind of microscope had just made visible.