310 EVENINGS AT THE MICROSCOPE 



than you would have supposed from looking at the tube; 

 and it is somewhat flattened, having a back and a belly 

 side. On the former there is a sort of shield, the sides of 

 which bear wart-like feet about seven pairs in all -which 

 are perforated for the working of protrusile pencils of 

 bristles, similar in structure and in function to those 

 which we lately examined. 



Here is one of the pencils extracted. To the naked 

 eye it is a yellowish body with a satiny lustre; and this 

 effect depends upon the light being reflected from a num- 

 ber of nearly parallel lines the staves of the spear-like 

 bristles, which the eye cannot resolve in detail. A drop 



of the caustic solution of potash cleanses the bundle from 

 the fleshy matter which would otherwise obscure the vision, 

 and now I place it on the stage. 



With this power of 400 diameters you see a multitude 

 some twenty or thirty, or more of very long, slender, 

 straight rods, of a clear yellowish horny substance, set 

 side by side, like a sheaf of spears in an armory. Each 

 one merges, at its upper end, into a sort of blade, wnich 

 is slightly bent, and which tapers to an exceedingly fine 

 point. But its chief peculiarity is that the blade has a 

 double edge, not like a two-edged sword, the edges set 

 on opposite faces, but on the same face, set side by side, 

 with a groove between them; and each edge is cut with 



