68 



THE SMALLEST LIVING THINGS 



vides, and the daughter cells then require some time before they 

 assume the characteristics of the species. 



Class Euglenineae 



This group, the Euglenida of protozoa, is another class of 

 plant flagellates, representative species being found everywhere in 



Fig. 35— A COMMON FLAGELLATE, 

 EUGLENA GRACILIS 



Photographed to show the length of the 

 flagellum 



From a photomicrograph by the author 

 Magnification, 950 



stagnant waters. They are quite complex structurally, but are 

 rarely colonial, the independent cells moving about by means of 

 one or sometimes two flagella. Green chlorophyll is present in 

 chromatophores, varying in number from one to many. Instead 

 of starch, prominent products of assimilation appear as solid, fre- 

 quently large, granules of paramylum* of diverse shapes (rods, 

 rings, disks, etc.). The individual cells vary in size from 15|-t 

 to \S0\i and are usually elongate and cylindrical with tapering to 

 pointed posterior ends. Euglena (Fig. 35), the commonest 

 genus, and many other related genera, have red eye-spots ;t Pha- 

 cus is flattened and has one central paramylum granule; Trache- 

 lomonas is enclosed in a shell which is often ornamented with 

 spines, or spiral ridges. Palmella states are common; the indi- 

 vidual discards its flagellum, becomes rounded, and secretes a 

 gelatinous envelope in which it divides. Many colorless types are 

 known, of which one of the commonest, Peranema, moves slowly 

 along the substratum* by means of a tiny whip lash (Fig. 36). 



* Paramylum is a carbohydrate, analogous to starch, but it does not stain with 

 iodine. 



t See the Glossary of this book, page 121. 



t Substratum, the substance or base upon which a plant grows. 



