Of the first group, Euglena (Fig. 9), may be selected as a type.
Many of these minute plants develop locomotion and a degree of sensitiveness (Diatoms, Peridinea, Euglena, etc.).
The principal species are the Euglena viridis and the Euglena pyrum.
In this way Engelmann was able to determine the evolution of oxygen by Euglena and by chlorophyl granules.
Among unicellular green alg, Chlamydomonas, has its maximal efficiency in the yellowish-green and Euglena in the blue.
Now, so far as we know, there is no natural limit to the existence of the Euglena, or of any other living germ.
Furthermore, the Euglena will increase in size; but this increase is by no means unlimited, as the increase of a crystal might be.
Astsia hmatdes (fig. 25), which is probably a form of the Euglena, is found in stagnant pools, which it renders red.
Euglena viridis the dabbler calls them, which seems unnecessary information.