Larry Burgess, age 14, of Peoria, Illinois for his question:
Is the euglena plant or animal?
Most people assume that they can tell the plants from the animals. The differences between a cow and a cowslip make a list as long as your arm. Few people confuse the cat and the catnip or the crow and the crocus, And if you are well traveled or well read you can tell the difference between a pecan and a toucan. But, down in the microscopic kingdom of one‑celled bodies, the difference between plant arid animal is not always so clear.
The euglena is one of these small controversial figures. He is claimed by both the botanists and the us‑ or at least by most of them. A few tired biologists leave him to botanists and a few over‑busy botanists leave him to them. Botany, of course, is the study of plant life and the study of animal life.
Both the plant kingdom and the animal kingdom are classed in huge groups or tribes called phyla, plural form of phylum. The phyla range from the most simple plant or animal life to the most complex. Phylum I of the plant kingdom is Protophyta ‑ the first plants. Phylum I of the animal kingdom is our Protozoa, meaning first life.
Protophyta and Protozoa include all the one‑celled plants and animals. Chances are we shall find the small euglena listed and fully described among the one‑celled plants and the one‑celled animals. In the plant world his family name is Euglenaceae, his order is Euglenales, his class is Flagellatae. In the animal world his family name is Euglenidae. His order is Euglenoidina and he is classed Phytomastigma. The little fellow has twice his share of fancy names.
Each of his scientific names gives a clue to his nature. Flagellatae tells us he has a whip‑tail or flagellum. Phytomastigma says he is a plant type with a whip‑tail. His name euglena means true eye pupil. The little fellow has an eye spot which is sensitive to light. He also expands and contracts his body as he moves, very much like our eye pupils react to light.
There are two vital questions for separating the microscopic plants from the microscopic animals. Does it move? If so, it is an animal. Does it have green chlorophyll? If so, it is a plant: Our little euglena answers yes to both questions. He moves and he has green chlorophyll.
The euglena has a long body, tapered at each end. Fair sized euglenas measure lp000 to an inch. Large fellows measure 500 to an inch. Each has a hollow gullet at one end from which grows the whip‑like flagellum. The little fellow moves through the water by squeezing and stretching his body and waving his tail. However, he follows his tail which is out in front.
The euglena’s body is filled with green chlorophyll and in the light he feeds like a plant, by photosynthesis. In the dark, however, he loses his green color and feeds by absorbing through his body surface. Hence you will meet the curious little euglena whether you study botany or biology.