QO LIGHT AND THE BEHAVIOR OF ORGANISMS 



few exceptions had none. The latter were considerably 

 smaller than the former. They averaged nearly 0.08 mm. 

 in length and somewhat more than 0.015 mm. in diameter. 

 A fairly good idea of the form and structure may be obtained 

 by referring to Fig. 10. It will be seen in this figure that 

 the caudal end terminates in a spinelike process, and that 

 the eye-spot, in close contact with the canal leading from 

 the contractile vacuole, forms an angle of about 45° with 

 the long axis of the body. The eye-spot has the form of a 

 flattened disk somewhat curved, so as to fit around the 

 canal. 



e. Method of locomotion. — It is frequently stated that 

 Euglenae in this state progress by amoeboid movements, 

 i.e., by streaming movements. I was, however, unable to 

 detect anything resembling streaming movements in any 

 of the several different species studied in the crawling state. 

 Many do change their form very much by contracting in 

 various ways, and some may move slightly by thrusting 

 the anterior end forward and then drawing up the posterior 

 end, but progression in this way is relatively unimportant. 



The process of locomotion without flagella appears to be 

 much the same in all forms observed. It was however 

 studied in detail only in Euglena x. While in motion these 

 organisms usually are considerably curved, being convex 

 on the ventral surface, the side opposite the eye-spot. 

 They rotate on the long axis either entirely over to the left, 

 as seen from the posterior end, or only halfway, then back 

 again, lying on the dorsal surface during this apparent 

 rocking movement. During either of these rotating move- 

 ments both ends appear to move back and forth. The 

 posterior end however moves laterally much less than the 

 anterior. In many instances it continues forward in nearly 

 a straight path, while the anterior end progresses on a 

 spiral course of considerable relative width. 



While thus rotating the organisms appear to slide along, 

 moving forward a little with each turn of the body. They 

 progress at the rate of about 0.3 mm. per minute. Pre- 



