Tue Microscope. 123 
cule’s substance and to be projecting posteriorly into the water 
beyond, but the appearance is illusory; the cuticular surface 
still surrounds the end of the frustule as a delicate film, and 
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he cilia continue in motion. At this stage I expected to see 
the diatom slip through the longitudinal interspaces in the rod 
—fascicle, but it did not; and this leads me to suppose that an 
invisible elastic membrane connects the rod-like elements. 
This slight obliquity of the pharnyx somewhat increased 
the pressure on the posterior cuticular surface and may have 
facilitated the next move, which was an unexpected one and 
the key to the problem. The entire pharynx suddenly rotated 
around the oral aperture as a center, turning itself upside down, 
the diatom slipping out, darting forward as it did so and pro- 
