ETE-SPOT AND ELAGELLUM IN EUGFjENA VIRIDIS. 475 



the light space, perhaps two or three layers deep, all of them 

 with the anterior end pointing downwards towards the source of 

 light. On turning down the condenser so as to get the light 

 spread evenly over the whole field of the microscope, they 

 begin at once to move away rapidly in all directions, and in one 

 or two minutes are found in all parts of the field. If the light 

 is again focussed upon a small portion of the field, the Euglence 

 turn round suddenly and make for it ; and a steady stream of 

 them will be seen moving up to the light from all parts of the 

 field. When the light space is shifted from place to place in 

 the field of the microscope, the Euglencs follow it ; and if the 

 mirror be moved backwards and forwards ia such a manner 

 that the light space is made to pass continually from one side of 

 the field to the other, the Euglencs arrange themselves ail across 

 the field in the area marked out by the passage to and fro of the 

 light space. The rapidity with which they move up to the light 

 space is much greater when there is no diaphragm over the con- 

 denser than when one is present. The diffuse light outside the 

 bright spot apparently guides them. 



It is interestiug to watch the movements of the Euglence in 

 the light space. The majority of them move about freely, but 

 iippear to be unable to get out ; for directly the anterior end of 

 an individual passes into the shade, it turns round completely 

 and goes back again into the light. Some of them, however, may 

 pass completely into the shade, and may even swim for some 

 distance into the dark part of the field before turning round ; 

 others again do not turn round completely at once, but move 

 round the edge of the light space in a tangential direction for 

 some distance before passing in again. 



Some of the cells which are strongly attracted to the light 

 space move straight across it, and pass out again on the opposite 

 side into the dark part of the field. After traversing this for 

 some distance, they turn round and repeat the performance; 

 and they may do this three or four times in succession before 

 they come to remain in the light space. 



If a drop of water containing motile Euglence be placed on a 

 glass slip and exposed to bright sunlight, the Euglence move to 

 that side which is farthest from the sun. If the slip is turned 

 round, they at once begin to move towards the opposite side, 

 that which is now farthest from the sun ; and in the space of 

 three minutes a large number of Euglencs are able to pass from 



