Introduction 



XV 



THE EUGLENA 



I have generally been able to get the Euglena by this 

 method :, place pieces of bark an inch or more square, 

 preferably from the edge of a pond, in the middle of a 

 beaker or jar holding a pint or more 

 of water. Set the culture vessel in a 

 north window and let it stand. In a 

 few weeks examine the upper and under 

 surfaces of the pieces on the bottom, 

 and you are likely to find Euglena 

 viridis. 



Euglenae are also likely to be found 

 on the sides and bottoms of many small 

 aquaria. I have had fine lots of them 

 develop in closed glass plant boxes, 

 which had been temporarily used for 

 keeping frogs. In small salt-water 

 aquaria containing horse-shoe crabs 

 they have also developed in great abun- 



'^'^^' _ The GRiiEN Euglena: 



I have also obtained a fine lot of Active form. Magni- 



Euglena viridis in this way : a glass ^ ' 

 dish two inches high by six inches in diameter was two- 

 thirds filled with vegetable debris — - largely pond scum — 

 from an old spring. It was then filled with water, covered, 

 and placed near a window. After standing undisturbed 

 nearly two months, a thick whitish scum had developed on 

 top, and on the sides of the dish at the surface of the 

 water there was a green growth composed almost entirely 

 of euglenae. 



In summer and autumn the standing water in the 

 vicinity of barnyards is frequently full of euglense in 



