Branch Protozoa 



THE EUGLENA 



The Euglena may be found in a resting or active condi- 

 tion ; if resting, its form is generally almost or quite spheri- 

 cal. In finding and studying it, use the high power of the 

 microscope. 



I. — Study the free-swimming movements of the active 

 organisms : do they always move straight ahead, or do 

 they sometimes twist and turn about .'' Watch the eugle- 

 noid contortions of the body ; make five outline sketches 

 showing the changes undergone by a single specimen. 

 See whether the shape assumed when swimming freely 

 straight ahead is generally the same in different indi- 

 viduals.- Distinguish between the anterior and poste- 

 rior ends of the body. Watch the animal turn round 

 and round on its longitudinal axis: does it show any 

 differentiation into dorsal and ventral regions .' 

 II. — The direct cause of locomotion will be found in the 

 constant vibratory movement of a single hair-Uke pro- 

 cess, about one-half as long as the body and projecting 

 from the anterior end. It is to be seen most plainly in 

 the largest specimens. This is the flag611um: it is a 

 part of the protoplasm of the body, differentiated for 

 the purpose of locomotion ; it is permanent in the active 

 form of the Euglena, and cannot be withdrawn Uke 

 the pseudopod of the Amoeba. By careful focussing, 

 one can get glimpses of the cone-like cavity with the 

 apex pointing inward, from the inner end of which 

 the flagellum arises. This cavity serves the purpose 

 of mouth and gullet, into which the vibration of the 

 flagellum brings particles that serve as food. See 

 the vortex in the water caused by the movement of 

 the flagellum. 



