124 EVENINGS AT THE MICROSCOPE. 



interrupted at its middle point ; and just there, in each 

 pro-leg, a clear vesicle or fleshy bladder protrudes from 

 the sole, which may perhaps serve as a very delicate organ 

 of touch, or may exude a viscid secretion helpful to pro- 

 gress on smooth bodies. The hooks seem adapted to 

 catch and hold the fine threads of silk, which most cater- 

 pillars spin as a carpet for their steps. 



In some cases the circle of hooks is complete, as in this 

 example, which I find in one of the slides of my drawer, 

 marked " Pro-leg of a Caterpillar." It is some large 

 species, probably a Sphinx, for the hooks are very large, 

 of a clear orange-brown hue, and set in a long oval ring 

 single as to their basis, but double as to their points 

 completely around the extremity of the foot. These hooks 

 belong only to the skin, as may be well seen in this pre- 

 pared specimen doubtless mounted in Canada balsam ; 

 for their roots are mere blunt points, set but little below 

 the surface of the thin skin without any enlargement or 

 apparent bulb. 



