124 The Microscope. 



in London were illuminated some years ago, in honour 

 of a distinguished visitor. It was not till I had 

 clearly ascertained that each jet was fixed, but sub- 

 jected to a whirling motion from the air, that I realized 

 that the whole thing did not turn on a central pivot. 



The expansion of a vorticella's cilia, after its sud- 

 den retreat and gradual emerging, can be detected by 

 a little practice and management of the microscope's 

 focus screw. It will swing its globular head into full 

 view, and suddenly its rim will open out, and the 

 fringe of cilia show for an instant in extreme delicacy ; 

 and then, off they go, in their rapid whirling move- 

 ment. 



The portly stentors, however, show the cilia in 

 splendid style. The one which is represented thim- 

 ble-shaped, and careering along at the right of No. 

 13, is using its cilia as paddles to propel it, while 

 the three temporarily fixed, and generally of trumpet 

 shape, are attracting food to their mouths. This 

 animalcule (that is to say, the bright green species 

 of stentor, Stentor polymorphus, or the many-shaped,) 

 is quite visible to the unassisted eye. They will 

 often occur in great numbers (and the same may be 

 said of other animalcules) in a piece of water on 

 one fishing occasion, and be quite scarce, or appa- 

 rently altogether absent, at another time. 



Number 4 is another animalcule. It is the 

 " bagpipe-like creature" of my list, and I believe 

 was Trachelius ovum. 



The " stiff- branched pillars," so described in my 

 list in contradistinction to the slender waving stem of 



