OBSERVATIONS ON UNICELLULAR FORMS 



8l 



plasts of various forms. They have a contractile vacuole 

 which opens to the exterior at the anterior end, and a brown 

 pigment spot known as the eye-spot, in close connection with 

 the vacuole. They exist m three states, — free-swimming, 

 crawling and encysted (Fig. lo). In the free-swimming 



C 'p 



F 



-0.01 mm. 



Fig. io. Sketches of Euglena, showing general structure of dififerent forms. 

 A and C, Euglena :*; sp. (?) in crawling state; B, probably a form of E. viridis; D, 

 E, E. deses; e, eye-spot; v, contractile vacuole; ch, chloroplasts; space in B limited 

 by dotted lines well filled with small chloroplasts; n, nucleus; c, caudal spine; p, 

 pigment granules which appear to be composed of same substances as eye-spot, 

 — these were found in only a few specimens. E, shows typical curvature toward 

 dorsal surface while swimming in direction indicated by arrow. F, eye-spot highly 

 magnified; s, surface view; a, view from anterior end. The convex surface is 

 directed outward, mm., projected scale. All outlines were made with camera 

 from specimens killed in iodine. Contractile vacuoles and nuclei were sketched 

 free-hand from Uving specimens. 



state they have a flagellum frequently nearly as long as 

 the body. Wager (1900) found that in E. viridis it passes 

 down through the opening of the contractile vacuole and 

 divides into two branches, each of which is attached to the 

 wall of the vacuole. One of these branches contains an 

 enlargement which lies directly opposite the eye-spot, as 



