76 BIOLOGY 



food and thus resembles Paramecium and the other animals 

 already described. 



EUQLENA 



Euglena (Fig. 29 B) greatly resembles Peranema in shape and 

 structure. Like the Peranema, it has an elongated body, taper- 

 ing, however, at both ends. One end carries a long, motile flagel- 

 lum by means of which the animal moves through the water. It 

 is made up of flexible protoplasm and goes through a series of 

 contorted motions similar to those seen in Peranema. One or 

 more contractile vacuoles are found near the base of the flagel- 

 lum. The animal moves about either by its flagellum or by the 

 creeping motion noticed in Peranema. It has also a reddish 

 "eye spot" near the front end. 



Evidently, these two organisms are very closely related. In 

 two respects, however, there is a striking difference, which has 

 led to the classification of the Euglena by some biologists among 

 the plants instead of among the animals. The Euglena probably 

 possesses no true mouth and does not take in solid food, though 

 this is disputed. Moreover, this animal is green, and since 

 green coloring matter is one of the distinctive characters of 

 plants, its presence in Euglena has led to much controversy 

 regarding the classification of this organism. Peranema with 

 its mouth and the animal habits should evidently be classed 

 with the animals, whereas Euglena, with its green color, would 

 naturally be classed with the plants; and yet their similarity 

 would lead to classing them together. A further consideration 

 of this subject will be given in a later chapter. 



PLANTS 



Although there is a difference of opinion in regard to the 

 classification of Euglena and Peranema, there is none in regard to 

 the organisms which are now to be described. The following 

 organisms are always recognized as plants, although some of 

 them, for reasons that will be given later, have certain charac- 



