340 Mr. H. J. Carter on the Ultimate 
contact with the glass cover, but soon sink to the plane of the 
slide, about which they move with the head foremost, apparently 
urged on in a zigzag course by the undulations of the cilium 
behind. For the most part they are single, 
a- 
gle, but occ 
sional groups of four are seen rolling over the field after the 
